Download ASSOCIATION OF PRENATAL ANDROGEN EXPOSURE WITH

ASSOCIATION OF PRENATAL ANDROGEN EXPOSURE
WITH ATTENTION AND SOCIOSEXUAL
ORIENTATION
A Thesis Presented to the Faculty
of
California State University, Stanislaus
In Partial Fulfillment
of the Requirements for the Degree
of Master of Arts in Psychology
By
Heather L. Strong
July 2014
CERTIFICATION OF APPROVAL
ASSOCIATION OF PRENATAL ANDROGEN EXPOSURE
WITH ATTENTION AND SOCIOSEXUAL
ORIENTATION
by
Heather L. Strong
Signed Certification of Approval Page is on
file with the University Library
Dr. Victor X. Luevano
Associate Professor of Psychology
Date
Dr. Dawn L. Strongin
Professor of Psychology
Date
Dr. Ana Marie Guichard
Associate Professor of Psychology
Date
© 2014
Heather L. Strong
ALL RIGHTS RESERVED
DEDICATION
To Mom, for all of the pride in education you have instilled in me. Because of
you, I understand the value of my work and the value of the teachers and professors
who have guided me to this point. Of all the teachers in my life, you have taught me
the most. Thank you.
iv
ACKNOWLEDGEMENTS
First and foremost, I would like to thank my thesis advisor, Dr. Victor X.
Luѐvano. I greatly appreciate his confidence in my abilities, which helped guide my
decision to pursue this degree. For that, I am forever grateful. I value him as teacher,
colleague, and friend, and look forward to working with him in the future.
I would also like to thank my thesis committee, Dr. Dawn Strongin and Dr.
AnaMarie Guichard. Not only have they been a great addition to the thesis writing
experience, but they have also been invaluable role models for me throughout my
entire experience with higher education. From the moment I met Dr. Strongin in
Intro to Psychology, I knew I was in the right place: a safe and humorous
environment with highly respectable and knowledgeable leaders. I thank my entire
thesis committee for the inspiring and encouraging roles they played in my education.
I thank the graduate and undergraduate research assistants who completed
data collection for this study. Their work and time is greatly appreciated.
Additionally, I thank the volunteers who posed as models for the eye-tracker stimuli.
v
TABLE OF CONTENTS
PAGE
Dedication ...............................................................................................................
iv
Acknowledgements .................................................................................................
v
List of Tables .......................................................................................................... viii
Abstract ...................................................................................................................
ix
Introduction .............................................................................................................
1
Organizational Hypothesis ..........................................................................
Prenatal Androgen Exposure and 2D:4D ....................................................
Inconsistencies in the Literature .................................................................
2D:4D and Women .....................................................................................
Sociosexual Orientation ..............................................................................
Eye Tracking Studies and Sex Differences .................................................
Competition.................................................................................................
Research Questions and Hypotheses ..........................................................
1
2
4
6
7
9
11
12
Method ....................................................................................................................
14
Participants ..................................................................................................
Measures .....................................................................................................
Procedure ....................................................................................................
14
15
18
Results .....................................................................................................................
20
Sex Differences in 2D:4D ...........................................................................
Participant Gender and Fixation on Male and Female Models...................
Sociosexual Orientation and 2D:4D ...........................................................
Correlations of Dating Ratings and SOI and 2D:4D ..................................
Multiple Regression ....................................................................................
Exploratory Analyses ..................................................................................
20
20
21
22
23
23
Discussion ...............................................................................................................
26
Sex Differences in 2D:4D ...........................................................................
Participant Gender and Fixation on Male and Female Models...................
Sociosexual Orientation and 2D:4D ...........................................................
Dating Ratings, Sociosexual Orientation, and 2D:4D ................................
26
27
29
31
vi
Fixation, 2D:4D, and Sociosexual Orientation ...........................................
Limitations ..................................................................................................
33
33
References ...............................................................................................................
38
Appendices
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
Photographic Stimuli ..................................................................................
Model Rating Questionnaire .......................................................................
Competition and Cooperation Games .........................................................
Sociosexual Orientation Inventory-Revised ...............................................
Demographics Questionnaire ......................................................................
Informed Consent Form ..............................................................................
Physiological Measures Form .....................................................................
Model Ranking............................................................................................
Mating Effort Scale .....................................................................................
Debriefing Form..........................................................................................
Annotated Bibliography ..............................................................................
vii
46
50
52
54
57
58
59
60
63
64
66
LIST OF TABLES
TABLE
PAGE
1. Means, Standard Deviations, and T-Tests for Men (n = 25) and Women’s (n = 45)
Fixation in Seconds on Male and Female Models ............................................
21
2. Zero-Order Correlations for All Variables .......................................................
22
viii
ABSTRACT
This study examined the relationships between 2D:4D (the ratio between the second
and fourth digits of the hand, which may be a marker of prenatal androgen exposure),
sociosexual orientation, and attention to photographic stimuli. The sample included
52 women and 31 men who were presented with photographs of men and women
while their gaze behavior was measured with an eye tracker. Participants indicated
which model was the most attractive, which was the greatest competition, and how
likely each model was to agree to date the participant. Contrary to previous research,
I found no significant gender differences between men and women’s right or left hand
2D:4D. Overall, male models received longer fixation than female models; this was
true for both male and female participants, although the relationship was not
significant among the men. Lower, more masculine, left hand 2D:4D was associated
with higher scores on the behavior subscale of the Sociosexual Orientation InventoryRevised. Participants who scored high on the desire and attitude subscale and global
sociosexual orientation were more confident in their ratings of how likely the models
would be to date them. 2D:4D and sociosexual orientation was not associated with
fixation on models deemed most attractive or highest in competition. This study
utilizes an uncommon procedure for evaluating mating behaviors. By combining eye
tracker data, a measure of prenatal androgen exposure, and a measure of sociosexual
orientation, this study has provided a multifaceted approach to the study of mating
behaviors.
ix
INTRODUCTION
Androgens, a class of sex steroids that include testosterone, have been linked
to several characteristics including, but not limited to, competition (Wilson, 1983),
muscle-mass (Nielson et al., 2010), and sociosexuality (Edelstein, Chopik, & Kean
2011). The ratio between the second and fourth digit of the hand (2D:4D) is easily
measured and is thought to reflect prenatal androgen exposure. 2D:4D has been
found to be associated with sexual orientation (Putz, Gaulin, Sporter, & McBurney,
2004), number of sexual partners (Honekopp, Voracek, & Manning, 2006), and
aggression (Honekopp, 2011). In the current study, I aim to address the relationship
between 2D:4D and mating behaviors and characteristics, such as sociosexuality, and
eye-gaze behavior. In doing this, I hope to add to the body of evidence in the current
research literature, which thus far seems inconclusive regarding the relationship of
2D:4D ratio to mating behaviors.
Organizational Hypothesis
The effects of early exposure to androgens is best explained by the
Organizational Hypothesis (Phoenix, Goy, Gerall, & Young, 1959), which states that
androgen exposure at important developmental stages can permanently alter the
structure and function of neural tissue involved in mating behaviors (Wallen, 2009).
The original theorists (Phoenix et al., 1959) observed that testosterone administered
to pregnant guinea pigs masculinized the genitalia of female offspring and altered the
mating behaviors of the offspring as adults. More recently, a review by Thornton,
1
2
Zehr, and Loose (2009) concluded that rhesus monkeys who receive prenatally
administered testosterone experience permanent masculinization of genitalia and
mating behaviors and that these changes occur only when testosterone is administered
at a maximally sensitive period during prenatal development.
Masculinization due to early androgen exposure may also be displayed in
humans. For example, girls with congenital adrenal hyperplasia (CAH) have
masculinized genitalia due to high levels of prenatal androgens (Nelson, 2005). In
these cases, the adrenal glands responsible for cortisol production instead produce an
abundance of androgens, resulting in genital masculinization. Boys may also
experience genital dysformities due to abnormal prenatal androgen function. The
androgen receptors of genetic males with androgen insensitivity syndrome (AIS) are
not functional, and thus their external genitalia is feminized (Nelson, 2005).
However, they do not possess a functional internal reproductive system. Though
uncommon, these examples demonstrate the organizing effects of prenatal androgen
exposure in humans.
Prenatal Androgen Exposure and 2D:4D
2D:4D measurement is the ratio between the length of the second and fourth
digit measured from the basal crease to the tip. It may be a predictor of prenatal
androgen exposure, with a lower ratio indicating higher levels of prenatal androgens
(Manning, Scutt, Wilson, & Lewis-Jones, 1998). It has been suggested that high
levels of prenatal androgens (testosterone) increase the length of the ring finger, while
high levels of estrogen increase the length of the index finger (Manning et al., 1998).
3
Low 2D:4D results from a shorter index finger in comparison to the ring finger and is
referred to as masculinized. In contrast, high 2D:4D results from a longer index
finger in comparison to the ring finger and is referred to as feminized.
Not surprisingly, men have lower 2D:4D ratios than women (Hönekopp &
Watson, 2010; Manning et al., 1998). The sensitivity of the androgen receptor gene
may play a role in the development of 2D:4D. Androgen sensitivity is determined by
the number of CAG (cytosine, adenine, guanine) repeats in the androgen receptor
gene. Lower numbers of repeats correspond with higher sensitivity to androgens,
while higher numbers of repeats correspond with lower sensitivity to androgens.
According to Manning, Bundred, Newton, and Flanagan (2004), prenatal androgen
sensitivity, as is determined by CAG repeat length in the androgen receptor gene,
contributes to 2D:4D. They found a positive correlation between 2D:4D
measurements and CAG repeat length, such that fewer CAG repeats (which are
associated with higher androgen sensitivity) corresponded with lower 2D:4D
measurements. In a study by Knickmeyer, Woolson, Hamer, Konneker, and Gilmore
(2011), it was found that testosterone measured at three months of age and CAG
repeat length alone were not significant predictors of 2D:4D in infants and toddlers.
However, the interaction of testosterone and CAG repeat length predicted 2D:4D in
12 and 24 month old males. In other words, those with both relatively high levels of
testosterone and relatively high sensitivity to androgens (i.e. low numbers of CAG
repeats) had lower 2D:4D ratios.
4
Manning et al. (1998) found a negative correlation between 2D:4D and sperm
count and testosterone, suggesting that lower 2D:4D is related to higher levels of
circulating testosterone and effects related to high testosterone levels, such as
spermatogenesis. This may suggest that those with high prenatal exposure to
androgens continue to have high testosterone levels as adults. Unlike circulating
levels of testosterone, which vary throughout the day and throughout development,
2D:4D ratios are constant and may be a more reliable measurement of androgen
action. However, it should be noted that free or serum levels of testosterone may
have activating effects that influence behavior, and exposure to prenatal androgens
alone does not necessarily affect behavior (Thornton et al., 2009).
Inconsistencies in the Literature
Multiple studies have found inconsistent or non-significant results regarding
the relationship between 2D:4D measurements, traits, and behaviors. Particularly,
there have been inconsistencies regarding which hand best predicts these outcomes.
Putz et al. (2004) found that left hand 2D:4D, but not right hand, was predictive of
sexual orientation. However, Manning et al. (2004) found a positive relationship
between CAG repeat length and right hand 2D:4D, but not left. Similarly, right hand
2D:4D is negatively associated with number of sexual partners, such that an
individual with lower, (masculinized) right hand 2D:4D has a higher number of
sexual partners than an individual with higher (feminized) 2D:4D (Hönekopp,
Voracek, & Manning, 2006). Hönekopp (2011) found that men’s left hand 2D:4D
was associated with verbal aggression while women’s right hand 2D:4D was
5
associated with risk-taking. Contradictorily, Hönekopp and Schuster (2009) found no
difference between left (N = 2,791) and right hand (N = 2,810) 2D:4D as predictors of
athletic prowess in a meta-analysis of 25 studies examining 2D:4D and athletic
ability. Though inconsistencies remain, a meta-analysis by Hönekopp and Watson
(2010) that consisted of 116 studies (11,789 men and 13,260 women) revealed that
the right hand is more sexually dimorphic (d = 0.457) than the left (d = 0.376), with
males having significantly lower right hand 2D:4D ratios (M = 0.959) than females
(M = 0.975). They suggest that the right hand may be more sensitive to prenatal
androgens, and thus a better representation of prenatal androgen exposure than the
left hand.
2D:4D is significantly correlated with sexual orientation in both men and
women, but it is not a valid predictor of many sexually dimorphic traits, such as
mental rotation (Putz, Gaulin, Sporter, & McBurney, 2004). However, Manning,
Churchill, and Peters (2007) found that heterosexual White males in both the United
States and United Kingdom had lower 2D:4D ratios than homosexual or bisexual
men, and no relationship was found for women or Black or Chinese male participants.
A study investigating 2D:4D in discordantly sexually oriented female twins found
that the homosexual twin had significantly lower 2D:4D than the heterosexual twin
(Hall & Love, 2003). A meta-analysis that examined 2D:4D and sexual orientation
found that homosexual women had lower 2D:4D ratios than heterosexual women,
while there was no significant difference in 2D:4D ratios between homosexual and
heterosexual men (Grimbos, Dawood, Burriss, Zucker, & Puts, 2010). Additionally,
6
it was found that homosexual men had lower 2D:4D ratios in samples with
predominantly White participants, while homosexual men had higher 2D:4D ratios in
samples that did not contain predominantly White participants.
2D:4D and Women
Women are rarely the focus of 2D:4D research, and the studies that have been
conducted with female participants yield inconsistent or non-significant results. In a
study examining masculine characteristics in women, it was found that women with
lower, more masculine, 2D:4D ratios were more likely to self-report being assertive
and competitive (Wilson, 1983). It is important to note, however, that finger
measurements were based on participants’ self-reports and may not accurately
represent 2D:4D ratios. As stated previously, homosexual women are more likely to
have lower, more masculine, 2D:4D than heterosexual women (Hall & Love, 2003).
Additionally, women who are more unrestricted in terms of uncommitted sexual
relationships have lower 2D:4D than women who are restricted (Clark, 2004).
Many studies that investigate the effects of 2D:4D on both men and women
find significant results for men and non-significant results for women. For example,
2D:4D was found to be negatively correlated with risk-taking behaviors in men, but
not in women (Stenstrom, Saad, Nepomuceno, & Mendenhall, 2011). Similar results
have been found for aggression (Honekopp, 2011). In addition, 2D:4D predicts hand
grip strength in men, but not women (Hone & McCullough, 2012). Finally, higher
2D:4D is associated with higher levels of openness in men, with a similar, but weaker
relationship in women (Burton, Guterman, & Baum, 2013).
7
Though 2D:4D may not be as predictive of characteristics in women as it is in
men, the small number of significant findings point to the possibility of early
androgenic effects on women’s mating behaviors in adulthood. Most importantly, for
purposes of this study, there have been significant findings regarding 2D:4D and
sociosexual orientation in women (Clark, 2004).
Sociosexual Orientation
Sociosexual orientation is a measure of how restrictive or unrestrictive
someone is in terms of attitudes, desires, and behaviors regarding uncommitted sex
(Penke & Asendorpf, 2008). It encompasses past unrestricted sexual experiences
(e.g. promiscuity), values placed on uncommitted sex and committed relationships,
and sexual interest in and fantasies about potential mating experiences that do not
occur in the context of a committed relationship. The three components of
sociosexuality—attitudes, desires, and behaviors—are interdependent, meaning one
component can affect the others (Penke & Asendorpf, 2008). However, the
components may not necessarily “match.” For example, someone may be
sociosexually unrestricted in regards to their attitudes and desires, but may have a
restricted sexual past due to the sociocultural environment they live in or the paucity
of potential mates available. Sociosexual orientation is a multifaceted construct that
is best evaluated and understood in terms of its multiple components.
In a study examining sociosexual orientation, short- and long-term
relationship orientation, and 2D:4D, it was found that men scored significantly higher
than women on short-term relationship orientation, sociosexual orientation, and sex
8
drive (Schwarz, Mustafić, Hassebrauck, & Jörg, 2011). Additionally, there was a
negative correlation between 2D:4D and short-term relationship orientation in men,
meaning that men with lower, more masculine, 2D:4D measurements were more
likely to report a short-term relationship orientation. However, there was no
significant relationship between 2D:4D and sociosexual orientation, which may be
due to the use of the unrevised global version of the Sociosexual Orientation
Inventory (SOI). The global SOI does not distinguish between the three facets of
sociosexual orientation: attitudes, beliefs, and behaviors.
The separate subscales of the SOI may better represent the nuances in
sociosexuality and examining the three factors separately may yield results that would
not be found with the global version of the SOI. In a study examining sociosexuality,
testosterone, and relationship status, Edelstein et al. (2011) found an association
between testosterone and men’s sociosexual desire and women’s sociosexual
behavior for partnered individuals. These differences would not have been found had
this study used the global version of the SOI.
Clark (2004) investigated a female sample in terms of sociosexual orientation,
attractiveness and 2D:4D and found that women who scored high on the SOI
(unrestricted) rated themselves higher in attractiveness and had lower 2D:4D ratios
than women who scored low on the SOI (restricted).
Sacco, Hugenberg, and Sefcek (2009) found that men and women with an
unrestricted sociosexual orientation were significantly better than those with a
restricted sociosexual orientation at distinguishing between genuine and deceptive
9
female smiles. The authors believe individuals who are unrestricted are better at
perceiving sexual cues, such as genuine smiles. Another study found that men who
are sociosexually unrestricted and women with an agreeable personality type are
more likely than their counterparts to accurately assess their own mate-value, which
was defined as potential mates’ interest in that person (Back, Penke, Schmukle, &
Asendorpf, 2011). Since the researchers found significant results for men, but not
women, regarding sociosexual orientation, I expect that relationships between my
study variables and sociosexual orientation may be stronger for men than women.
Eye Tracking Studies and Sex Differences
An important aspect of the current study is to examine fixation behavior while
participants view pictures of potential partners and how these behaviors relate to
2D:4D measurements. One previous eye-tracker study examining the differences
between men and women while viewing sexual stimuli found that women looked at
female faces for a shorter time than men (Rupp & Wallen, 2006), which may be due
to women’s ability to interpret emotional stimuli (i.e. facial expressions) more
quickly (Hampson, van Anders, & Mullin, 2006). Rupp and Wallen’s (2006) study
also compared women using and not using oral contraceptives and found a difference
in their look patterns, suggesting a hormonal influence on attention.
Another eye-tracker study measured men and women’s gaze while viewing
pictures of male and female models, either clothed or nude, and found that men
looked at female models for a longer period of time than they looked at male models,
and women looked at male and female models equally (Nummenmaa, Hietanen,
10
Santtila, & Hyona, 2012). It was also found that faces were examined for the longest
period of time and typically were the first fixation. Consistent with these findings,
two studies found that while participants viewed pictures of men and women in
casual attire, the first fixation was always on the face (Alexander & Charles, 2009;
Hewig, Trippe, Hecht, Straube, & Miltner, 2008). Hewig et al. (2008) compared gaze
patterns of heterosexual men and women and found that men tend to look at the
breast region of males and females sooner than women do, and fixate on the female
breast region for a longer amount of time than women do.
In a study by Levy et al. (2008), men and women were presented with pictures
of male and female faces and were told to press certain keys to view the picture for a
longer or shorter amount of time, indicating their interest and the attractiveness value
of the target. It was found that men preferred to view pictures of females for a longer
amount of time than pictures of males, while women preferred to look at both genders
for equal amounts of time. Weege, Lange, and Fink (2012) measured women’s gaze
patterns while viewing dancing male avatars and found that women spent more time
viewing the dancers they perceived to be attractive. Features that cue mate value for
females (youth, sexual maturity, and health) and males (dominance and status) are
viewed more frequently and before other features (Hassebrauck, 1998). Based on
these findings, I predict that participants will dedicate their gaze to the model of the
other sex that they deem the most attractive and the model of the same sex that they
deem their biggest competition in obtaining a mate (also likely to be the model
thought to be the most attractive).
11
Competition
Another important aspect of the current study is examining participants’
fixation on people who they rate as their competition in a mating situation. In a crosscultural study that measured the physical strength of male and female American,
Andean, and Tsimane volunteers, it was found that the volunteers’ actual strength was
positively correlated with American college students’ impressions of the volunteers’
strength based on facial photographs alone (Sell et al., 2008). Impressions of strength
and impressions of fighting ability were highly correlated for pictures of males. The
authors postulate that it is important for men to accurately assess the strength of other
men as they would likely be competition, while it is important for women to
accurately assess the strength of men as potential mates.
Rosvall (2011) argues that women, like men, participate in intrasexual
competition. While men compete for quantity of mates, women compete for quality
of mates. Competition is highest among women when the operational sex ratio is low
(more women than men in a population). Given that the sex ratio is currently low at
CSU Stanislaus, I predict that intrasexual competition among the female participants
and models will be at least as high as that of male participants, in that female
participants will rate the female models at least as high in competition as male
participants rate the male models. This will be examined for exploratory analysis.
Female intrasexual competition is further supported by a study that examined
attractiveness and threat evaluations of pictures representing a woman attempting to
poach a potential male mate from the female participant (Fink, Klappauf, Brewer, &
12
Shackelford, 2013). It was found that poachers with more feminine faces, larger
breasts, and lower waist-to-hip ratios were rated as the highest threat and rated as
more attractive and feminine. Women tend to compete with other women who pose
the greatest threat to their reproductive success. Though models in the current study
are not posing an actual threat to participants, the models will be rated on their level
of competition based on their looks. The amount of attention paid to the model
participants deem to be highest in competition will be examined.
Research Questions and Hypotheses
Question I: How does 2D:4D differ between men and women? I predict that men
will have lower 2D:4D ratios than women.
Question II: Will there be a sex difference in fixation? I predict that there will be a
sex difference in fixation, such that men will fixate more often and longer on female
models, and women will fixate on male and female models equally. I predict that
men and women with lower 2D:4D will exhibit a more masculine viewing pattern and
fixate on the models of the preferred sex.
Question III: What is the relationship between 2D:4D measurements and SOI
subscales and global scores? I predict that men and women with lower 2D:4D
measurements will be more likely to score as unrestricted, while those with higher
2D:4D measurements will be more likely to score as restricted.
Question IV: How do ratings of how likely models are to date the participant relate to
2D:4D and SOI scores? I predict that men and women with lower 2D:4D
measurements and higher SOI scores will be more confident in their rating of how
13
likely models would be to date them. Global scores and subscales scores of the SOI
will be examined.
Question V: How do 2D:4D measurements and SOI scores relate to fixation? I
predict a positive correlation between SOI scores and fixation on the model deemed
most attractive, and the model deemed highest in competition. I predict a negative
correlation between 2D:4D and fixation on the model deemed most attractive, and the
model deemed highest in competition.
METHOD
My thesis represents a portion of a larger study investigating the variables I’ve
described, along with additional physiological measures and measures of competition
and cooperation. Measures and materials not associated with my thesis will be very
briefly described in this section, with more detailed information provided in the
appendix.
Participants
The sample consisted of 31 men and 52 women between the ages of 18 and 47
(M = 21.64, SD = 4.88) recruited from the online psychology research participant
pool at a small university in the San Joaquin Valley and from fliers posted on campus.
Participants had the choice of receiving either extra credit or a ten dollar gift card as
compensation for their participation.
Ethnicities of participants included 52.3% Hispanic, 21.6% White, 11.4%
Asian/Pacific Islander, 3.4% Black, 1.1% American Indian/Alaskan Native, and 5.7%
other. All participants reported at least one sexual partner within the past 12 months.
One male participant with previous injuries to the second left digit was excluded from
2D:4D analysis. Three male and three female participants who were acquainted with
the models who posed for the stimuli photographs were also excluded from analysis.
An additional three male and four female participants were excluded from eye-tracker
analysis due to mistakes in coding. Therefore, 2D:4D analyses were conducted for 30
14
15
men and 52 women, and eye-tracker analyses were conducted for 25 men and 45
women.
Measures
2D:4D Measurements
The second and fourth digit of both the right and left hands were measured
from the basal crease to the tip by a trained research assistant using a Vernier caliper.
Grip Strength
Grip strength was measured via a hand dynamometer. Participants were
instructed to stand and hold the dynamometer at their side while gripping the handle
tightly, twice for each hand. Grip strength was measured for exploratory analysis and
for future studies.
CAG Repeat Length of the Androgen Receptor Gene
Participants used a swab to collect buccal cell samples from the inside of their
cheek. This DNA sample was collected to obtain CAG repeat length measurements
for future analysis.
Photographic Stimuli
Twenty-six photographs were presented on the eye-tracker screen.
Photographs included five men and five women in their twenties in casual party attire.
The models were in various couple and group combinations and each model appeared
in a total of eight photographs. Photographs were presented one at a time for seven
seconds each while participants’ eye gaze behavior was recorded via the eye-tracker
(Appendix A).
16
Model Ratings Questionnaire
This questionnaire was created for the purpose of this study (Appendix B). A
portrait of one model from the previous stimuli was presented with a brief rating
questionnaire online. Participants rated each model on a seven-point Likert scale for
three different questions. The questions included, “How attractive do you find this
person?” (1 = not at all attractive, 7 = very attractive), “Would you consider this
person competition for obtaining a mate?” (1 = not at all, 7 = very much so), “How
likely do you think this person is to date you?” (1 = not at all likely, 7 = very likely),
and “How well do you know this person?” (have never seen them, have seen them
around, acquaintance, know them well). Data from six participants who were
acquainted with or knew a model well were excluded from analysis.
Additionally, participants indicated which model they found most attractive
and the most competition for a mate. Fixation in milliseconds for the model ranked
highest in attraction and the model ranked highest in competition were defined as
attention to attraction and competition, respectively. Ratings of how likely the model
would be to date the participant were combined across all models of the participants’
preferred gender to obtain a dating confidence score.
Competition and Cooperation Games
Two games were used for the purpose of measuring competition and
cooperation for the general study, but are not assessed in this thesis. The first was the
Point Subtraction Aggression Paradigm (Golomb, Cortez-Perez, Jaworski, Mednick,
17
& Dimsdale, 2007), followed by an established public goods game (Van Vugt, De
Cremer, & Janssen, 2007). See Appendix C for more detail.
Sociosexual Orientation Inventory-Revised
The original Sociosexual Orientation Inventory (SOI) was created by Simpson
and Gangestad (1991) and was a seven-item global measure of one’s willingness to
engage in uncommitted sexual relationships. The Sociosexual Orientation InventoryRevised (SOI-R) (Penke & Asendorpf, 2008) separates the original SOI into three
distinct components of sociosexuality: behaviors, attitudes, and desires. Each
subscale contains three items for a total of nine-items. Internal reliability of the SOIR is sufficiently high for the current study, global scores α = .71, behavior subscale α
= .78, attitude subscale α = .86, and desire subscale α = .86.
Behavior was measured with three questions, such as, “With how many
partners have you had sex with in the past 12 months?” All behavior items measure
number of sexual partners regarding the behavior listed and range from 0 to 20 or
more. Attitude was measured with three items on a slider scale that ranged from 0
(strongly disagree) to 100 (strongly agree). For example, an item that measures
attitude was, “Sex without love is OK.” Question six (“I do not want to have sex with
a person until I am sure that we will have a long-term relationship”) is part of the
attitude subscale and was the only reverse coded item. Desire measured the
frequency of fantasies and arousal and was measured by three questions such as,
“How often do you have sexual fantasies about having sex with someone whom you
do not have a committed romantic relationship?” Answers on this subscale ranged
18
from never to at least once a day. High scores on the SOI-R indicate an unrestricted
sociosexuality (willingness to engage in uncommitted sex) and lower scores indicate
a restricted sociosexuality (unwillingness to engage in uncommitted sex) (Appendix
D).
Demographics Questionnaire
The demographics questionnaire was created for the purpose of this study.
Participants reported information about their gender, age, ethnicity, sexual
orientation, and relationship status (Appendix E).
Procedure
Appointments were scheduled online and sessions took place on the CSU
Stanislaus campus. Participants completed the study one at a time with one research
assistant in a small room with a computer and eye-tracker. All surveys and games
were completed on a computer. Upon arrival, participants were informed about the
procedure of the study and signed an informed consent form (Appendix F). The
research assistant then measured the second and fourth digits of each hand, following
the protocol described above, then measured the grip strength of each hand
(Appendix G). Buccal cell samples were then collected.
Participants then sat at the eye-tracker and completed a calibration task to
ensure eye gaze movement was properly measured. They were then informed that
they were about to view a series of pictures of people at a party in a bar and to
imagine that they were at that same party. Eye movements were recorded as
participants viewed the 26 photographs previously described. After viewing the
19
photographs, participants were disconnected from the eye-tracker and shown a picture
of each model individually, on the computer. They then completed the model rating
questionnaire for each model. Participants were then presented with a page
containing all of the individual model portraits and were prompted to choose the one
model they believed was the most attractive, the one model they believed was their
highest competition in attracting a mate, and the one model they believed would be
the most likely to date them (Appendix H). Fixation time in seconds for these
particular models was used as the measure of competition, attraction, and attention to
best mating opportunity.
Participants then completed the SOI-R, Mating Effort Scale (Rowe, Vazsonyi,
& Figueredo, 1997) (Appendix I), and demographics questionnaire. All
questionnaires were completed anonymously online through Qualtrics. Participants
were then fully debriefed and given the opportunity to choose between extra credit for
a psychology course or a ten dollar gift card as their compensation for participation
(Appendix J).
RESULTS
Sex Differences in 2D:4D
I predicted that there would be a difference between men and women’s 2D:4D
measurements. Contrary to my prediction, an independent groups t-test revealed no
significant difference between men’s left hand 2D:4D (n = 31, M = 0.97, SD = 0.04)
and women’s left hand 2D:4D (n = 51, M = 0.96, SD = 0.04), t(79) = 0.70, p = .486, d
= 0.16, 95% CI [-0.29, 0.61]. Although the right hand has been found to be more
sexually dimorphic (Hönekopp & Watson, 2010) than the left, I found no significant
difference between men’s right hand 2D:4D (M = 0.98, SD = 0.04) and women’s right
hand 2D:4D (M = 0.97, SD = 0.04), t(79) = 0.61, p = .547, d = 0.14, 95% CI [-0.31,
0.59].
Participant Gender and Fixation on Male and Female Models
I used a mixed model ANOVA to examine the effects of participant sex and
model sex on fixation time. A main effect was found for fixation on male and female
models, such that, overall, male models received an average of 7.11 more seconds of
fixation than female models, F(1, 68) = 9.03, p = .004, η² = .117 (see Table 1).
There was no main effect of sex of the participant, F(1, 68) = 1.12, p = .293, η² =
.016. There was not a significant interaction between participant sex and sex of the
models on fixation time, F(1, 68) = 1.22, p = .273, η² = .018.
Contrary to my hypothesis that women would fixate on male and female
models equally, a mixed model ANOVA revealed simple effects of model gender for
20
21
female participants, such that women fixated on male models 9.74 seconds longer
than they fixated on female models, F(1, 68) = 11.83, p = .001, η² = .148 (see Table
1). I predicted that men would fixate longer on female models than male models;
however, this was not supported, F(1, 68) = 1.40, p = .241, η² = .020 (see Table 1).
Table 1
Means, Standard Deviations, and T-Tests for Men (n = 25) and Women’s (n = 45)
Fixation in Seconds on Male and Female Models
Male Models
Female Models
M
SD
M
SD
t
Cohen’s d
Men
79.57
18.91
74.07
19.81
1.00
0.22
Women
84.45
11.88
74.71
14.11
3.89**
0.75
Total
82.35
14.92
74.48
16.24
3.50*
0.50
Note. *p = .001, **p < .001
I hypothesized that men and women with lower 2D:4D would exhibit a more
masculine viewing pattern, such that they would fixate longer on models of the
preferred sex. Pearson’s zero order correlations did not support this hypothesis, ps >
.60.
Sociosexual Orientation and 2D:4D
Pearson’s zero-order correlations were used to determine the relationship
between 2D:4D and sociosexual orientation. I predicted that men and women with
lower, more masculine, 2D:4D would score higher (unrestricted) on the SOI. This
was only marginally significant for left hand 2D:4D and the behavior subscale, r(83)
= -.21, p = .062. See Table 2 for full correlation table.
22
Table 2
Zero-Order Correlations for All Variables
1.
2.
3.
4.
5.
6.
7.
8.
9.
1. L2D:4D
-
-
-
-
-
-
-
-
-
2. R2D:4D
.28*
-
-
-
-
-
-
-
-
3. G. SOI
-.08
.02
-
-
-
-
-
-
-
4. Behavior
-.21†
-.07
.60**
-
-
-
-
-
-
5. Attitude
-.07
.02
.99**
.57**
-
-
-
-
-
6. Desire
-.00
-.01
.73**
.40**
.69**
-
-
-
-
7. Fix. A.
.12
.12
-.01
.10
-.09
-.04
-
-
-
8. Fix. C.
.03
-.03
-.12
-.06
-.12
-.07
.01
-
-
9. Fix. D.
.14
-.05
-.13
-.01
-.12
-.03
.76**
.02
-
10. T. date
-.08
-.05
.14
.18
.13
.26*
.03
.06
.04
Note. L2D:4D and R2D:4D stand for left and right hand 2D:4D, respectively. G. SOI is an
abbreviation for global SOI scores. Behavior, attitude, and desire represent the three subscales of the
SOI. Fix. A., Fix. B., and Fix. C. are abbreviations for fixation time on most attractive, fixation time
on highest competition, and fixation time on most likely to date, respectively. T. date is the total
score for participants’ ratings of how likely each model is to date the participant.
†p < .10, *p < .05, **p < .001
Correlations of Dating Ratings and SOI and 2D:4D
I predicted that men and women with lower, more masculine 2D:4D and men
and women who scored as unrestricted on the SOI and its subscales would be more
confident in their ratings of how likely the models would be to date them.
Participants rated each model on a scale of one (not at all likely) to seven (very
likely). A variable was created that represented the total score of dating likelihood for
23
each participant. Pearson’s zero-order correlations revealed that participants who
scored high on the desire subscale were more confident in their ratings of how likely
the models would be to date them, r(78) = .26, p = .022. No significant correlations
were observed for dating likelihood and right or left hand 2D:4D (see Table 2).
Multiple Regression
Multiple regression was used to determine the relationship between fixation
on the most attractive and 2D:4D and SOI, as well as fixation on the highest
competition and 2D:4D and SOI. I predicted that men and women with lower, more
masculine, 2D:4D and higher scores on the SOI would fixate on models they deemed
the most attractive and the highest competition for a longer amount of time.
Attention to the most attractive model was marginally predicted by scores on the
behavior subscale (β = .29, p = .069), but not attitude scores (β = -.31, p = .130), or
desire scores (β = .07, p = .714). Including all of the SOI subscales and 2D:4D of
each hand altogether as predictors did not significantly predict fixation time on the
most attractive, (ΔR² = .068, F(5, 65) = 0.95, p = .457) or highest competition (ΔR² =
.013, F(5, 71) = 0.19, p = .967).
Exploratory Analyses
Further analysis revealed that women tended to fixate on the model they
deemed the most attractive 3.06 seconds longer than men fixated on the model they
deemed the most attractive, t(68) = 1.99, p = .050, d = .50, 95% CI [-0.00, 0.99].
When participants acquainted with models were included, a slightly stronger
relationship was found, such that women tended to fixate on the model they deemed
24
the most attractive 3.23 seconds longer than men fixated on the model they deemed
the most attractive, t(74) = 2.26, p = .027, d = .54, 95% CI [0.06, 1.01].
A paired samples t-test revealed that women fixated on the model deemed the
most attractive (M = 19.38, SD = 5.86) significantly longer than the model deemed
highest in competition (M = 14.78, SD = 4.27), t(44) = 9.93, p < .001, d = .90, 95%
CI [2.24, 6.96]. This relationship was not found for men, t(24) = 0.59, p = .561, d =
.13, 95% CI [-3.59, 2.11].
Independent groups t-tests revealed a marginally significant finding that
women fixated longer on the model deemed most likely to date them (M = 17.59, SD
= 5.05) as compared to men (M = 15.20, SD = 4.88), t(63) = -1.87, p = .067, d = .45.
There was no significant difference between men (M = 15.48, SD = 5.13) and women
(M = 14.78, SD = 4.27) for fixation time on the highest competition model, t(68) =
0.61, p = .544, d = .15. However, when competition ratings were totaled,
independent groups t-tests revealed a marginally significant sex difference in
competition ratings, such that women rated the models higher in competition (M =
30.55, SD = 14.62) than men did (M = 24.29, SD = 10.80), t(75) = -1.98, p = .052, d =
.47.
When participants who were acquainted with models were included in
analysis, Pearson’s zero-order correlations revealed marginally significant positive
relationships between ratings of dating likelihood and global SOI scores (r(84) = .20,
p = .076), and the attitude subscale (r(84) = .18, p = .097). Participants who scored
25
high on the desire subscale were more confident in their ratings of how likely the
models would be to date them, r(84) = .28, p = .011.
Pearson’s zero-order correlations revealed that participants who scored high
on the Mating Effort Scale also scored high on global sociosexual orientation (r(84) =
.36, p = .001), the attitude subscale (r(84) = .34, p = .001), and the desire subscale
(r(84) = .43, p < .001). A marginally significant positive correlation was found for
the behavior subscale and scores on the Mating Effort Scale, r(84) = .19, p = .081.
However, reliability analysis revealed that the Mating Effort Scale did not have
sufficient internal consistency, α = .498.
DISCUSSION
Sex Differences in 2D:4D
Although I predicted a significant difference between men and women’s
2D:4D, this was not found. This finding was surprising, since much of the literature
posits that men and women differ significantly in 2D:4D, such that men have lower,
more masculine 2D:4D than women (see Hönekopp & Watson, 2001 for a review). I
believe this was due to human error in 2D:4D measurements for my sample.
Following the completion of data collection, two research assistants were instructed
to measure the 2D:4D of a man and woman. When the measurements were
compared, there was a large discrepancy between each research assistants’
measurements. Sufficient inter-rater reliability was not reached between research
assistants and thus 2D:4D measurements of participants are likely not accurate.
Future research should establish inter-rater reliability early on and frequently
throughout data collection.
However, it may be possible that my sample simply did not contain men and
women with average male and female 2D:4D ratios. It may be, by chance, that my
sample is not representative of the general population. Measurements may have been
accurate and discordant from the norm. However, this cannot be verified without
sufficient inter-rater reliability and thus neither of these two possibilities can be ruled
out.
26
27
Participant Gender and Fixation on Male and Female Models
Previous research has found a sex difference in fixation such that men tend to
fixate on female models for a longer amount of time than they fixate on male models,
and women tend to fixate on male and female models equally (Levy et al., 2008;
Nummenmaa, Hietanen, Santtila, & Hyona, 2012). Surprisingly, my results do not
agree with these previous findings. I found that women tended to fixate on male
models for a longer amount of time than they fixated on female models, men’s
fixation time on male and female models did not differ, and overall, male models
were viewed longer than female models.
I postulate that the reason previous research has found that men tend to look at
female models longer than they tend to look at male models (assuming that the men
are heterosexual) is due to their higher attraction to female than male models. My
sample contained three homosexual men and one bisexual man, who may not have
been attracted to the female models and thus, may have fixated longer on male
models. However, I completed the analyses without these participants to examine if
this was the case, but there were no significant changes in the results. Additionally,
my sample contained three homosexual women and two bisexual women. Similarly,
excluding them from analysis made no significant changes in results.
Further analysis revealed that women tended to fixate on the model they
deemed the most attractive longer than men fixated on the model they deemed the
most attractive. Since the majority of the female participants were heterosexual, this
seems to account for why women fixated longer on men. Simply put, women tended
28
to fixate on male models longer than they fixated on female models as a function of
attraction.
Given that explanation, shouldn’t men have also fixated on the sex they were
attracted to longer than the sex they were not attracted to? This was not supported as
men’s fixation time on male and female models did not differ. It may be that men
attend to their competition (other men) as much as they attend to women they’re
attracted to.
To my knowledge, past eye-tracking research has not distinguished between
attraction and competition. My research may suggest that there are subtle differences
in fixation between men and women, such that women are more likely to fixate on
models they are attracted to more than they fixate on competition. Whereas men are
more likely to fixate on people they deem their competition and people they deem
attractive a near equal amount, with a slight tendency to fixate on those they deem
high in competition.
A study conducted by Hill (2007) examined whether or not men and women
overestimated the desirability of same-sex models. A group of men and women rated
opposite sex models on their desirability, then a separate group of men and women
rated the same models (but this time the same sex) on desirability. Hill found that
men and women both tend to overestimate the desirability of members of their same
sex, thus they overestimate their competition. While this relationship was significant
for both sexes, it was a bit stronger for men. This may indicate that men are more apt
to be threatened by their competition because they deem them more desirable than
29
they are. Although the men in my sample did not show a significant difference in
fixation on competition and attraction, women showed a much larger difference, such
that they fixated longer on the model deemed the most attractive as compared to the
model deemed highest in competition. This may show that men are more threatened
by competition than women.
There may be an alternate explanation as to why men did not fixate on female
models longer than male models, as was hypothesized. Hassebrauck (1998)
conducted a study that utilized an alternative to eye tracking, called the Visual
Process Method (VPM). VPM is a process whereby participants view outlines of
male and female models and choose which body or facial portion to reveal in order to
make a judgment about physical attractiveness in the fewest amount of steps. The
entire picture was revealed and participants were timed (unknowingly) as they made a
final judgment on the models attractiveness. Hassebrauck found that men required
significantly less time to judge female models than women required to judge male
models. It may be that the men in my sample could quickly judge female
attractiveness and thus fixated on female models for a shorter amount of time than
was expected.
Sociosexual Orientation and 2D:4D
I predicted that those who scored high (unrestricted) on sociosexual
orientation would have lower, more masculine, 2D:4D. In accordance with my
hypothesis, those with lower left hand 2D:4D scored as unrestricted on the behavior
subscale of the SOI. The negative trend may suggest that those with lower, more
30
masculine, 2D:4D have a more unrestricted sociosexual orientation in terms of
behavior.
It is important to note that the separation of the SOI into three distinct
categories provides a more nuanced and specific look at sociosexual orientation. My
results support Penke and Asendorpf’s (2008) suggestion that sociosexual orientation
consists of multiple factors and is better analyzed using the three subscales, versus a
global score alone.
My findings are consistent with previous research that show a negative
relationship between 2D:4D and number of sexual partners (Hönekopp, Voracek, &
Manning, 2006). Simply put, those with more masculine 2D:4D tend to have more
sexual partners. My results support this since the behavior subscale of the SOI
(which was negatively correlated with 2D:4D) measures the number of recent sexual
partners. However, contrary to Hönekopp et al.’s (2006) findings that right hand
2D:4D was negatively associated with number of sexual partners, I found a
significant relationship for left hand 2D:4D only.
It is surprising that left, and not right, hand 2D:4D was negatively correlated
with the behavior subscale. Past research indicates that the right hand is more
sexually dimorphic and correlates more strongly with outcomes than does the left
hand (Hönekopp and Watson, 2010). As stated previously, it is possible that the
2D:4D measurements obtained for this study were not entirely accurate, and that may
account for the lack of significant results found for the right hand. However, it is also
a possibility that my sample simply is not representative of past findings. If the
31
measurements were accurate, it is possible that the left hand was a better predictor
than the right hand in this particular sample.
Though the right hand has been shown to be more sexually dimorphic (and
thus may be more sensitive to prenatal androgen exposure), there are previous studies
that have shown significant relationships with study variables and left hand 2D:4D
(Hönekopp, 2011; Putz et al., 2004). Therefore, the left hand may also be indicative
of prenatal androgen exposure, though it is not as strongly correlated as the right hand
in the majority of studies.
Dating Ratings, Sociosexual Orientation, and 2D:4D
Participants indicated how likely each model was to date them on a scale of
one to seven. Higher scores indicated more confidence that models would date the
participant. Those who scored high on the desire subscale of the SOI had higher
dating ratings, such that they were more confident that the models would agree to
date them.
Previous research has found that sociosexually unrestricted men are better at
determining if a potential mate is interested in them (Back, Penke, Schmukle, &
Asendorpf, 2011). Though the dating situation was hypothetical in my study, it may
be that participants who are more sociosexually unrestricted exhibit higher mating
effort (as is demonstrated in my exploratory analysis) and may feel more confident in
their overall ability to assess mating interest. These sociosexually unrestricted
participants may have felt more confident that the models in the pictures would agree
to go on a date with them. Participants who scored as sociosexually restricted
32
exhibited less mating effort, and may therefore not be as confident as their
unrestricted counterparts in a dating situation, even when hypothetical.
Interestingly, scores on the behavior subscale were not associated with dating
confidence. It would seem that this confidence would be due to successful dating
endeavors, which may be interpreted as sociosexual behavior. It is possible that
participants were not entirely comfortable with the questionnaire and didn’t answer
the behavior portion of the SOI honestly. Additionally, the term “dating” does not
necessarily imply sexual activity. Participants may have successfully acquired dating
partners in the past that didn’t result in sexual activity, and thus they may not have
had high scores on the behavior subscale.
On the other hand, participants may not have consistent ideas of what sexual
intercourse is and may have under- or over-reported their number of sexual partners
(i.e. the behavior subscale). A study investigating terms and context that qualified
individuals as sexual partners found that the only situation in which all participants
agreed two hypothetical people were sexual partners was when they engaged in
vaginal intercourse several times for at least three months (Cecil, Bogart, Wagstaff,
Pinkerton, & Abramson, 2001). All forms of sex listed (vaginal, anal, and oral) were
unlikely to qualify the partners as sexual partners if the act occurred one time only.
Because the behavior subscale inquires about sex that occurred one time only, it is
very likely that participants in my sample under-reported the number of sexual
partners due to inconsistent definitions of sex.
33
Exploratory analyses revealed that, when participants who were acquainted
with models were included, sociosexual orientation was positively associated with
dating confidence. This may suggest that dating confidence is increased when a
person has actually interacted with the potential partner, versus only seeing them in a
picture.
Contrary to the SOI, 2D:4D was not associated with dating ratings. This may
be due to human error in 2D:4D measurements which may have resulted in inaccurate
measurements. It may also be possible that prenatal androgen exposure is not
associated with later dating confidence.
Fixation, 2D:4D, and Sociosexual Orientation
I hypothesized that those with lower, more masculine, 2D:4D and unrestricted
sociosexuality would fixate on the models they deemed the most attractive and
highest in competition for a longer amount of time. However, this was not supported
by my analysis. It may be that sociosexual orientation and 2D:4D are not predictors
of attention; rather, gender plays a more important role. I found that women tended
to fixate longer than men on the model they deemed the most attractive.
Limitations
As stated previously, the largest limitation of this study was the possibility
that 2D:4D measurements were inaccurate. This may be due to insufficient training.
In the future, all research assistants should be trained by the same person, and
multiple checks of inter-rater reliability for all research assistants throughout the
course of data collection should occur. Additionally, it may be beneficial to acquire
34
scans of participants’ hands which could then be measured by multiple researchers at
the completion of data collection. These later measurements should be compared to
the live measurements obtained by research assistants to ensure proper calculations.
An additional limitation was the wording of the behavior subscale of the SOI.
Each question refers to sexual intercourse, but does not provide a specific definition
for what sexual intercourse entails. As stated previously, there is little agreement
about what qualifies as sex, and the discrepancies between participants’ views about
sex may yield inaccurate results. In the future, it would be beneficial to provide a list
of acts that qualify as sex so participants will answer consistently.
Though a strength of the current study was the use of an eye-tracker to
measure unconscious attention to potential mates and competition, there are
limitations associated with this kind of research. First, the dating situation
participants were told to imagine themselves in was purely hypothetical. Though I
attempted to create a context with high ecological validity, I was not able to achieve a
true representation of a live mating context.
Second, participants’ eye movements and fixation on pictures of models may
not accurately reflect these behaviors in real life situations. It is likely that
participants, as part of a media viewing population, are accustomed to viewing
pictures of models and these viewing patterns of pictures may not accurately reflect
eye movements directed toward live people.
Next, fixation times may not be entirely accurate, as it is possible that the first
fixation of each picture was in the same area of the last fixation of the previous
35
picture. Future research should include a cross image between each picture, which
the participant is instructed to fixate on. This cross (or any shape) should be placed
on an area of the screen, such as a top or bottom corner, not in an area of interest. In
doing so, the occurrences of accidental fixations would be decreased.
Finally, the lack of consistency between model poses, facial expressions, and
clothing may be a limitation. In an effort to increase ecological validity, I sacrificed
control. Future research should include both ecological pictures, as well as
controlled, consistent pictures of models. These types of pictures should then be
compared to examine which form (ecological or controlled) is more useful as eyetracker stimuli.
In addition to the methodological limitations listed above, there were also
participant limitations. Ideally, the samples of men and women should have been
more balanced. My sample contained considerably more women than men, however,
the sample sizes were large enough to be compared confidently. Unfortunately, the
sample sizes of homosexual and bisexual participants were too small to compare to
the heterosexual sample. In the future, researchers should make a stronger effort to
recruit homosexual and bisexual participants so they can be included in research and
not labeled as confounds. Additionally, it is important to further research the role
2D:4D plays in sexual orientation, as it is not yet fully defined.
Despite the methodological and participant limitations listed, this study
provides support for the further research of 2D:4D and variables related to it.
Measurements of 2D:4D need to be collected carefully and the procedure must be
36
perfected in order to draw sound conclusions. This study utilized a novel procedure
for measuring competition and attraction within a mating context. Unconscious eyemovements may be a more accurate representation of mating behavior as compared to
participant self-report alone. By combining eye-tracker data with self-report data and
physiological measurements, I hope to have created a multifaceted approach to the
study of mating behavior.
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38
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41
men. Psychoneuroendocrinology, 31, 30-37.
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Hönekopp, J., & Watson, S. (2010). Meta-analysis of digit ratio 2D:4D shows greater
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Official Journal of the Human Biology Council, 22, 619-630.
doi:10.1002/ajhb.21054
Knickmeyer, R. C., Woolson, S., Hamer, R. M., Konneker, T., & Gilmore, J. H.
(2011). 2D:4D ratios in the first 2 years of life: Stability and relation to
testosterone exposure and sensitivity. Hormones and Behavior, 60, 256-263.
doi:10.1016/j.yhbeh.2011.05.009
Levy, B., Ariely, D., Mazar, N., Chi, W., Lukas, S., & Elman, I. (2008). Gender
differences in the motivational processing of facial beauty. Learning and
Motivation, 39, 136–145.
Manning, J. T., Bundred, P. E., Newton, D. J., & Flanagan, B. F. (2004). The second
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Human Behavior, 24, 399-405. doi:10.1916/S1090-5138(03)00052-7
Manning, J. T., Scutt, D., Wilson, J., & Lewis-Jones, D. I. (1998). The ratio of 2nd to
4th digit length: A predictor of sperm numbers and concentrations of
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more differentiated look at sociosexuality and its effects on courtship and
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44
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APPENDICES
46
APPENDIX A
PHOTOGRAPHIC STIMULI
47
48
49
50
APPENDIX B
MODEL RATINGS QUESTIONNAIRE
How attractive do you find this person?
Not at all attractive
1
2
Very Attractive
3
4
5
6
7
Would you consider this person competition for obtaining a mate?
Not at all
1
Very much so
2
3
4
5
6
7
51
How likely do you think this person is to date you?
Not at all likely
1
2
Very likely
3
4
5
6
7
How well do you know this person?
___ Have never seen them ___ Have seen them around ___ Acquaintance
___ Know them well
52
APPENDIX C
COMPETITION AND COOPERATION GAMES
Two games were used for the purpose of measuring competition and
cooperation for the general study, but are not assessed in this thesis. The first was the
Point Subtraction Aggression Paradigm (Golomb, Cortez-Perez, Jaworski, Mednick,
& Dimsdale, 2007), followed by an established public goods game (Van Vugt, De
Cremer, & Janssen, 2007). The point subtraction game was intended to create a
rivalry. Participants were told they would be playing an online game with a student,
named Player 47, from a different campus. In reality, the game was preprogrammed
and the participant was playing against the computer. The goal of the game was to
obtain as many points as possible by either clicking on a plus sign (to gain points),
clicking on a minus sign to take away (but not gain) points from the opponent, or
clicking the block icon to protect their point bank from the rival. Regardless of the
participants’ strategy, the computer always won, and thus Player 47 became a rival.
The second game, a public goods game, was played immediately after the first
and was designed to measure cooperation and competition. Like the first game, the
public goods game was preprogrammed and played online with fictitious players.
The purpose of the game is to collect as many tokens as possible for the team. Players
were asked to put tokens into the group pot, which would then be doubled and split
evenly among all players. Personal contributions to the pot were confidential. There
were five total players, including the participant, who each started the game with
53
twenty tokens. Players had the option of how many tokens to place in the group pot.
Placing more tokens in the pot is beneficial for the group, while keeping tokens is
beneficial for only that player. After a practice round, the research assistant then
pointed out that Player 47, the participant’s rival from the previous game, was either
on their team or on the opposing team, based on random assignment. Participants
then played the game.
To incentivize serious participation in this game, participants were told they
would receive one raffle ticket per token they collected, which would be drawn from
a raffle for a $50 gift card. They were also told that the team with highest number of
tokens would receive an additional gift. In reality, every participant received on one
raffle ticket and thus has an equal chance of winning the $50 gift card. Since the
teams were fictitious, there was no additional prize for the winning team.
54
APPENDIX D
SOCIOSEXUAL ORIENTATION INVENTORY-REVISED
Please respond honestly to the following questions:
1. With how many different partners have you had sex within the past 12
months?
□
□
□
□
□
□
□
□
□
0
1
2
3
4
5-6
7-9
10-19
20 or
more
2. With how many different partners have you had sexual intercourse on
one and only one occasion?
□
□
□
□
□
□
□
□
□
0
1
2
3
4
5-6
7-9
10-19
20 or
more
3. With how many different partners have you had sexual intercourse
without having an interest in a long-term committed relationship with
this person?
□
□
□
□
□
□
□
□
□
0
1
2
3
4
5-6
7-9
10-19
20 or
more
4. Sex without love is OK.
55
1□
2□
3□
4□
5□
6□
7□
Strongly
8□
9□
Strongly agree
disagree
5. I can imagine myself being comfortable and enjoying "casual" sex with
different partners.
1□
2□
3□
4□
5□
6□
7□
Strongly
8□
9□
Strongly agree
disagree
6. I do not want to have sex with a person until I am sure that we will
have a long-term, serious relationship.
1□
2□
3□
4□
5□
6□
7□
Strongly
8□
9□
Strongly agree
disagree
7. How often do you have fantasies about having sex with someone you
are not in a committed romantic relationship with?
□ 1 – never
□ 2 – very seldom
□ 3 – about once every two or three months
□ 4 – about once a month
□ 5 – about once every two weeks
□ 6 – about once a week
□ 7 – several times per week
□ 8 – nearly every day
56
□ 9 – at least once a day
8. How often do you experience sexual arousal when you are in contact
with someone you are not in a committed romantic relationship with?
□ 1 – never
□ 2 – very seldom
□ 3 – about once every two or three months
□ 4 – about once a month
□ 5 – about once every two weeks
□ 6 – about once a week
□ 7 – several times per week
□ 8 – nearly every day
□ 9 – at least once a day
9. In everyday life, how often do you have spontaneous fantasies about
having sex with someone you have just met?
□ 1 – never
□ 2 – very seldom
□ 3 – about once every two or three months
□ 4 – about once a month
□ 5 – about once every two weeks
□ 6 – about once a week
□ 7 – several times per week
□ 8 – nearly every day
□ 9 – at least once a day
57
APPENDIX E
DEMOGRAPHICS QUESTIONNAIRE
1. What is your gender? _____ Male _____ Female _____ Other
2. How old are you? ________ years
3. Which of the following best describes your current relationship status?
_________ single
_________ dating (in one or more non-committed relationship)
_________ in a committed relationship
_________ engaged
_________ married
_________ divorced
_________ widower
4. Which best describes your sexual orientation?
____ heterosexual ___bisexual ____ homosexual
5. Which ethnic group do you identify with the most?
____ American Indian / Alaskan Native
____ Asian / Pacific Islander
____ Black, Non-Hispanic
____ Hispanic
____ White, Non-Hispanic
____ Other ________________________
58
APPENDIX F
INFORMED CONSENT FORM
Dear Participant:
You are being asked to participate in a research project. We are examining the
relationships among genes, behavior, personality, and attitudes. If you decide to
volunteer, you will be asked to provide a cheek swab, have your hands measured,
watch a slideshow of pictures, play a couple of short online games, and fill out a
questionnaire which includes questions of a personal nature (e.g. your attitudes
toward sexual behavior). Please do not participate in this study if you are not
comfortable with these types of questions.
There are no known risks to you for your participation in this study. However, your
participation in this study may lead to increased stress during the course of the study.
It is possible that you will not benefit directly by participating in this study. The
information collected will be protected from all inappropriate disclosure under the
law. All data will be kept in a secure location.
There is no cost to you beyond the time and effort required to complete the
procedure(s) described above. The procedure should take about one hour to complete.
Your participation entitles you to either 3 credits through SONA-system in the
Department of Psychology and Child Development at CSU Stanislaus, or a $10 gift
card. If you withdraw from the study, you are entitled to an amount proportional to
the amount of the study you complete. Your participation is voluntary. Refusal to
participate in this study will involve no penalty or loss of benefits. You may withdraw
at any time without penalty or loss of benefits.
If you are at least 18 years of age, and agree to participate, please indicate this
decision by signing below. If you have any questions about this research project
please contact Dr. Victor Luevano at [email protected] or (209)667-3096. If you
have any questions regarding your rights and participation as a research subject,
please contact the Campus Compliance Officer by phone (209)667-3794 or email
[email protected].
________________________________________
Participant Signature
_________________
Date
59
APPENDIX G
PHYSIOLOGICAL MEASURES FORM
Participant number: ___________________
Grip strength left 1: _____________ Grip strength right 1: _____________
Grip strength left 2: _____________ Grip strength right 2: _____________
Left index finger length: ___________Right index finger length: __________
Left ring finger length: ___________ Right ring finger length: __________
60
APPENDIX H
MODEL RANKING
Click on the photo of the one person you are most attracted to.
61
Click on the photo of the one person that you think would be your biggest
competition in attracting a mate.
62
Click on the photo of the one person that you think would be most likely to agree to
go on a date with you.
63
APPENDIX I
MATING EFFORT SCALE (ROWE, VAZSONYI, & FIGUEREDO, 1997)*
Agreement for all items is given on a 5-point scale (1= strongly disagree, 5= strongly
agree)
1. When I see someone I think is attractive with their significant other, I might try to
get their attention.
2. I would rather date several people at once than just one person.
3. I think the opposite sex finds me naturally attractive.
4. I like members of the opposite sex more for their good looks than for their
companionship.
5. I would get back at someone who looked at my significant other in the wrong way.
6. I would start a relationship with another person before ending my current
relationship.
7. My friends respect me because they know I’m a little wild and crazy.
8. If other members of my sex think I am attractive to the opposite sex, they will stay
away from my significant other.
9. Other members of my sex respect me because they know I have a lot of friends
who would support me.
10. If other members of my sex think I am tough, they will stay away from my
significant other.
*The Mating Effort Scale (Rowe, Vazsonyi, & Figueredo, 1997) is designed to
measure mating effort in males. The scale was modified for the current study to apply
to both males and females.
64
APPENDIX J
DEBRIEFING FORM
Thank you for participating in our study. We are interested in learning how genetics
are related to attention, personality, and behavior. We will use the cheek swab to
examine one specific gene. This gene is involved in regulating sensitivity to
chemicals in your body like testosterone. We have reason to believe that this gene
will be associated with who people pay attention to in the photos, and how people
answer the questionnaire. We also think this gene will be associated with people’s
competitiveness and willingness to cooperate with others. These were assessed with
the two games that you played.
In both games, you were not actually playing with or against any other people. The
other responses were all pre-programed. As a result, there is no way to actually link
the number of entries for the $50 drawing with your performance. Each participant in
this study will have an equal chance of winning.
All information collected in this study will be kept safe from inappropriate disclosure,
and there will be no way of identifying your responses, or biological measures, in the
data archive. Our measures of genetic information cannot be used to diagnose or treat
any disease or medical condition. Furthermore, we are not interested in anyone’s
individual responses; rather, we want to look at the general patterns that emerge when
all of the participants’ responses are put together. We ask that you do not discuss the
nature of the study with others who may later participate in it, as this could affect the
validity of our research conclusion. If you have any questions about your rights as a
participant in this study, please contact the Campus Compliance Officer at
209.667.3747.
If participating in the study caused you any concern, anxiety, or distress, you may
contact the Student Counseling Center at (209) 667-3381.
Thank you again for your participation. If you would like more information about this
study, please contact Dr. Victor Luevano at [email protected].
If you are interested in learning more about this research topic, we recommend the
following references:
Simmons, Z. L., & Roney, J. R. (2011). Variation in CAG repeat length of the
androgen receptor gene predicts variables associated with intrasexual
competitiveness in human males. Hormones and Behavior, 60, 306–312.
doi:10.1016/j.yhbeh.2011.06.006
65
Van Vugt, M., De Cremer, D., & Janssen, D. P. (2007). Gender differences in
cooperation and competition: The male-warrior hypothesis. Psychological
Science, 18, 19–23.
66
APPENDIX K
ANNOTATED BIBLIOGRAPHY
REFERENCES
The remaining pages summarize articles relevant to this thesis. Annotations
referenced in the text are marked by an asterisk.
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doi:10.1016/j.evolhumbehav.2006.05.002
*Hassebrauck, M. (1998). The visual process method: A new method to study
physical attractiveness. Evolution and Human Behavior, 19, 111-123.
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*Hewig, J., Trippe, R. H., Hecht, H., Straube, T., & Miltner, W. H. R. Gender
differences for specific body regions when looking at men and women.
(2008). Journal of Nonverbal Behavior, 32, 67-78. doi: 10.1007/s10919-0070043-5
*Hill, S. E. (2007). Overestimation bias in mate competition. Evolution and Human
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(but not hand grip endurance) in men (but not in women). Evolution and
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68
*Hönekopp, J. (2011). Relationships between digit ratio 2D:4D and self-reported
aggression and risk taking in an online study. Personality and Individual
Differences, 51, 77-80. doi:10.1016/j.paid.2011.03.010
*Hönekopp, J., & Schuster, M. (2010). A meta-analysis on 2D:4D and athletic
prowess: Substantial relationships but neither hand out-predicts the other.
Personality and Individual Differences, 48, 4-10.
doi:10.1016/j.paid.2009.08.009
*Hönekopp, J., Voracek, M., & Manning, J. T. (2006). 2nd to 4th digit ratio (2D:4D)
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*Hönekopp, J., & Watson, S. (2010). Meta-analysis of digit ratio 2D:4D shows
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Huh, H. (2013). Digit ratios, but not facial width-to-height ratios, are associated with
the priority placed on attending to faces versus bodies. Personality and
Individual Differences, 54, 133-136. doi:10.1016/j.paid.2012.08.032
*Knickmeyer, R. C., Woolson, S., Hamer, R. M., Konneker, T., & Gilmore, J. H.
(2011). 2D:4D ratios in the first 2 years of life: Stability and relation to
testosterone exposure and sensitivity. Hormones and Behavior, 60, 256-263.
doi:10.1016/j.yhbeh.2011.05.009
*Levy, B., Ariely, D., Mazar, N., Chi, W., Lukas, S., & Elman, I. (2008). Gender
differences in the motivational processing of facial beauty. Learning and
Motivation, 39, 136–145.
Loehlin, J. C., Spurdle, A., Treloar, S. A, & Martin, N. G. (1999). Number of Xlinked androgen receptor gene CAG repeats and femininity in women.
Personality and Individual Differences, 27, 887-899. doi:10.1016/S01918869(99)00038-0
Lukaszewski, A. W., & Roney, J. R. (2011). The origins of extraversion: Joint effects
of facultative calibration and genetic polymorphism. Personality and Social
Psychology Bulletin, 37, 409-421. doi:10.1177/0146167210397209
*Manning, J. T., Bundred, P. E., Newton, D. J., & Flanagan, B. F. (2004). The second
to fourth digit ratio and variation in the androgen receptor gene. Evolution and
Human Behavior, 24, 399-405. doi:10.1916/S1090-5138(03)00052-7
*Manning, J. T., Scutt, D., Wilson, J., & Lewis-Jones, D. I. (1998). The ratio of 2nd to
4th digit length: A predictor of sperm numbers and concentrations of
testosterone, luteinizing hormone and oestrogen. Human Reproduction, 13,
3000-3004.
Manuck, S. B., Marsland, A. L., Flory, J. D., Gorka, A., Ferrell, R. E., & Hariri, A. R.
(2010). Salivary testosterone and a trinucleotide (CAG) length polymorphism
in the androgen receptor gene predict amygdala reactivity in men.
Psychoneuroendocrinology, 35, 94-104. doi:10.1016/j.psyneuen.2009.04.013
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Medland, S. E., Duffy, D. L., Spurdle, A. B., Wright, M. J., Geffen, G. M.,
Montgomery, G. W., & Martin, N. G. (2005). Opposite effects of androgen
receptor CAG repeat length on increased risk of left-handedness in males and
females. Behavior Genetics, 35, 735-744. doi:10.1007/s10519-005-6187-3
*Nielsen, T. L., Hagen, C., Wraae, K., Bathum, L., Larsen, R., & Brixen, K. (2010).
The impact of the CAG repeat polymorphism of the androgen receptor gene
on muscle and adipose tissues in 20–29-year-old Danish men: Odense
Androgen Study. European Journal of Endocrinology, 162, 795-804. doi:
10.1530/EJE-09-0763
*Nummenmaa, L., Hietanen, J. K., Santtila, P., & Hyona, J. (2012). Gender and
visibility of sexual cues influence eye movements while viewing faces and
bodies. Archives of Sexual Behavior, 41, 1439-1451. doi:10.1007/s10508-0129911-0
Pasterski, V., Hindmarsh, P., Geffner, M., Brook, C., Brain, C., & Hines, M. (2007).
Increased aggression and activity level in 3- to 11-year-old girls with
congenital adrenal hyperplasia (CAH). Hormones and Behavior, 52, 368-374.
doi:10.1016/j.yhbeh.2007.05.015
*Penke, L., & Asendorpf, J. B. (2008). Beyond global sociosexual orientations: A
more differentiated look at sociosexuality and its effects on courtship and
romantic relationships. Journal of Personality and Social Psychology, 95,
1113-1135. doi:10.1037/0022-3514.95.5.1113
Perrin, J. S., Herve, P.-Y., Leonard, G., Perron, M., Pike, G. B., … Paus, T. (2008).
Growth of white matter in the adolescent brain: Role of testosterone and
androgen receptor. The Journal of Neuroscience, 28, 9519-9524.
doi:10.1523/JNEUROSCI.1212-08.2008
*Phoenix, C. H., Goy, R. W., Gerall, A. A., & Young, W. C. (1959). Organizing
action of prenatally administered testosterone propionate on the tissues
mediating mating behavior in the female guinea pig. Endocrinology, 65, 369382.
*Putz, D. A., Gaulin, J. C., Sporter, R. J., & McBurney, D. H. (2004). Sex hormones
and finger length: What does 2D:4D indicate? Evolution and Human
Behavior, 25, 182-199. doi:10.1016/j.evolhumbehav.2004.03.005
Rammsayer, T. H., & Troche, S. J. (2007). Sexual dimorphism in second-to-fourth
digit ratio and its relation to gender-role orientation in males and females.
Personality and Individual Differences, 42, 911-920.
doi:10.1016/j.paid.2006.09.002
*Rosvall, K. A. (2011). Intrasexual competition in females: Evidence for sexual
selection? Behavioral Ecology, 22, 1131-1140. doi: 10.1093/beheco/arr106
*Rowe, D., Vazsonyi, A., Figueredo, A. (1997). Mating-effort in adolescence: A
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*Rupp, H., & Wallen, K. (2007). Sex differences in viewing sexual stimuli: An eyetracking study in men and women. Hormones and Behavior, 51, 524-533.
doi:10.1016/j.yhbeh.2007.01.008
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*Sacco, D. F., Hugenberg, K., & Sefcek, J. A. (2009). Sociosexuality and face
perception: Unrestricted sexual orientation facilitates sensitivity to female
facial cues. Personality and Individual Differences, 47, 777-782.
doi:10.1016/j.paid.2009.06.021
*Schwarz, S., Mustafić, M., Hassebrauck, M., & Jörg, J. (2011). Short- and LongTerm Relationship Orientation and 2D:4D finger-length ratio. Archives of
Sexual Behavior, 40, 565-574. doi:10.1007/s10508-010-9698-9
*Sell, A., Cosmides, L., Tooby, J., Sznycer, D., von Rueden, C., & Gurven, M.
(2010) Human adaptations for the visual assessment of strength and fighting
ability from the body and face. Proceedings of the Royal Society, 276, 575584. doi:10.1098/rspb.2008.1177
*Simpson, J. A., & Gangestad, S. W. (1991). Individual differences in sociosexuality:
Evidence for convergent and discriminant validity. Journal of Personality and
Social Psychology, 60, 870-883. doi:10.1037/0022-3514.60.6.870
*Stenstrom, E., Saad, G., Nepomuceno, M. V., & Mendenhall, Z. (2011).
Testosterone and domain-specific risk: Digit ratios (2D:4D and rel2) as
predictors of recreational, financial, and social risk-taking behaviors.
Personality and Individual Differences, 51, 412-416.
doi:10.1016/j.paid.2010.07.003
*Thornton, J., Zehr, J. L., & Loose, M. D. (2009). Effects of prenatal androgens on
rhesus monkeys: A model system to explore the organizational hypothesis in
primates. Hormones and Behavior, 55, 633-645.
doi:10.1016/j.yhbeh.2009.03.015
Turakulov, R., Jorm, A. F., Jacomb, P. A., Tan, X., & Easteal, S. (2004). Association
of dopamine-b-hydroxylase and androgen receptor gene polymorphisms with
Eysenck’s P and other personality traits. Personality and Individual
Differences, 37, 191-202. doi:10.1016/j.paid.2003.08.011
Von Eckardstein, S., Syska, A., Gromoll, J., Kamischke, A., Simoni, M., &
Nieschlag, E. (2001). Inverse correlation between sperm concentration and
number of androgen receptor CAG repeats in normal men. The Journal of
Clinical Endocrinology and Metabolism, 86, 2585-2590.
*Weege, B., Lange, B. P., & Fink, B. (2012). Women’s visual attention to variation in
men’s dance quality. Personality and Individual Differences, 53, 236-240.
doi:10.1016/j.paid.2012.03.011
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*Alexander, G. M., & Charles, N. (2009). Sex differences in adults’ relative visual
interest in female and male faces, toys, and play styles. Archives of Sexual
Behavior, 38, 434-441. doi:10.1007/s10508-008-9429-7
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research was to test if men prefer to attend to female faces and if women
prefer to attend to male faces, based on fixation behavior as measured by an eyetracker. Additionally, it was hypothesized that men would direct their attention to
male-typical toys, and women would direct their attention to female-typical toys.
- Method: Participants included 44 women and 39 men between the ages of 18 and 25
years old from Texas A&M University. They were calibrated to the eye-tracker and
then viewed 12 pairs of pictures (each picture was displayed twice for a total of 24
stimuli pictures) depicting a gender specific toy, a black-and-white drawing of
gender-specific play behavior, or a photograph of an attractive male or female face.
Each pair of pictures was presented for five seconds and fixations and total time
viewing areas of interest were measured.
- Results: It was found that men fixated on female faces significantly more than male
faces, but there was no significant association between women and the gender of the
faces they tended to fixate on. Similarly, men preferred to fixate on male-typical play
styles, while no significant results were found for women’s fixation preference for
play-styles. Men fixated more on male-typical toys than women did, and women
fixated more on female-typical toys than men did. A positive correlation was found
between men’s fixation on female-typical toys and male faces.
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- Limitations/strengths: The most obvious limitation of this study is the lack of
information regarding participants’ sexual orientation. The introduction and
discussion both point to sexual orientation as a factor related to male and female face
preference and toy preference, yet it is not analyzed in the study. It is likely that
homosexual and heterosexual participants may fixate on same-sex faces, as those are
the faces they would be attracted to. However, a strength of the study is that the
authors did provide alternate explanations, besides sexual orientation, that may
account for the observed sex differences. Men are geared toward competition and
thus more attracted to pictures of potential mates and more aggressive, male-typical
toys and play styles. In contrast, women are geared toward tending and befriending
and may look at male and female faces equally as a means to increase her social
network, and prefer female-typical toys because they promote nurturance.
- Relevance: This study is relevant to my thesis because it found a significant
difference in male female fixation patterns in terms of fixation on male and female
faces. Though it was not measured, the authors suggest that early preference for
gender-specific toys may be related to early hormone exposure. It could be that
differences in fixation for male and female faces, and gender-specific toys and play
styles were not a function of gender alone. Rather, there may have been an effect of
early androgen exposure or sexual orientation that accounted for observed
differences, both of which I assess in my thesis.
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*Back, M. D., Penke, L., Schmukle, S. C., & Asendorpf, J. B. (2011). Knowing your
own mate value: Sex-specific personality effects on the accuracy of expected
mate choices. Psychological Science, 22, 984-989.
doi:10.1177/0956797611414725
- Article type/purpose/theoretical orientation/research questions: This primary
research article aimed to address differences in men and women who can accurately
assess their own mate value. Since men tend to prefer short-term mating strategies, it
was hypothesized that men who scored as sociosexually unrestricted would be better
than their restricted counterparts at determining their own mate value. Women,
however, tend to prefer long-term mating strategies, which require trust and
cooperation. Therefore, the authors predicted that women who scored high on the
personality trait agreeableness would be better than their non-agreeable counterparts
at determining their own mate-value.
- Method: Participants included 190 men and 192 women between the ages of 18 and
54 years old who participated in the Berlin Speed Dating Study. Before attending the
speed dating sessions, participants completed the NEO Five-Factor Inventory and the
revised version of the Sociosexual Orientation Inventory. Participants attended a total
of 17 speed-dating sessions that included between 17 and 27 men and women of
roughly the same age. For each speed dating session, the women were seated at a
booth and each man at the session would rotate booths until each man interacted with
each woman. Each date lasted a total of three minutes and interested partners were
able to exchange contact information. After each “date” participants indicated
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whether or not they wanted to see that person again and whether or not that person
wanted to see them again. Actual mate value represented the proportion of potential
mates who actually wanted to see the participant again divided by the total number of
interactions. Expected mate-value was defined as the proportion of potential mates
the participant expected to want to see them again divided by the total number of
interactions. The variable mate-value accuracy was calculated as the strength of the
relationship between actual mate-value and expected mate-value.
-Results: Overall, there was a sex difference in sociosexuality and agreeableness such
that men were more sociosexually unrestricted and less agreeable than women. Actual
and expected mate-value did not differ between men and women, and both men and
women, in general, could not accurately assess their own mate-value. Women who
scored as restricted showed a higher correlation between expected and actual mate
value than women who scored as unrestricted. Consistent with the hypotheses, men
who scored as unrestricted were better at assessing their actual mate-value than men
who scored as restricted, and women who scored as agreeable were better at
determining their actual-mate value than women who scored as non-agreeable.
- Limitations/strengths: A strength of this study is that it was the first to investigate
individual differences in mate-value accuracy. Additionally, this study has high
external validity since it utilized real speed-dating interactions. However, this study
contains limitations. The authors did not measure attractiveness, which has been
shown to play a role in mate selection, such that those with near-equal attractiveness
tend to pair up. It may be that those who accurately assessed their own mate-value
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were more aware of their own attractiveness, and thus better at determining potential
mates based on similar attractiveness.
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Baghaei, F., Rosmond, R., Landén M., Westberg,L., Hellstrand, M., Holm, G., …
Björntorp, P. (2003). Phenotypic and genotypic characteristics of women in
relation to personality traits. International Journal of Behavioral Medicine,
10, 364-378. doi:10.1207/S15327558IJBM1004_6
- Article type/purpose/theoretical orientation/research questions: This primary
research article aimed to investigate the relationship between androgens and
masculine-feminine characteristics in women and hypothesized that women with
higher androgen levels and/or sensitivity to androgens would score higher on
masculine traits.
- Method: 42 premenopausal Swedish women completed a masculinity-femininity
questionnaire that assessed dominance (masculinity), tenderness (femininity), and
neutral items. A physical examination was performed on all participants and blood
samples were collected to measure serum testosterone, CAG repeat length, and
cortisol. Participants also provided information about their SES, smoking and
drinking habits, birth weight, play behavior as children, and age of menarche.
- Results: Three times more women scored as masculine versus feminine, regardless
of CAG repeat length. Women who had more CAG repeats scored higher on
masculine traits, such as independence, dominance, leadership, and determination.
The authors also found that these characteristics were demonstrated very early-on in
life of the participants, thus they believe the women with more CAG repeats were
genetically predisposed to these characteristics. Androgen, cortisol, and estrogen
levels did not differ between the short and long repeat groups.
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- Limitations/strengths: A limitation of this study was the use of stereotypically
masculine and feminine characteristics. The authors believe that this measure is no
longer appropriate for modern-day women because the large majority of women now
exhibit male-typical characteristics. A strength of this study is that it examined
masculine and feminine factors in childhood, as well as adulthood. This helped
support the notion of genetic predisposition to masculinity or femininity.
- Relevance: This study provides information that supports the idea that women with
more CAG repeat lengths exhibit more masculine characteristics. These findings
contradict Loehlin et al., however, the measures of masculinity are quite different in
both studies. Reservation (masculinity in Loehlin et al.) is very different than
leadership, and dominance (masculinity in Baghaei et al.). However, these findings
are still consistent with the hypothesis that women with fewer CAG repeats (i.e.
reserved) will be less competitive than women with more CAG repeats (i.e.
dominant).
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*Burton, L. A., Guterman, E., & Baum, G. (2013). Effect of prenatal androgen on
adult personality: Greater openness with more female-typical 2D:4D digit
ratios. Current Psychology: A Journal For Diverse Perspectives On Diverse
Psychological Issues, 32(2), 197-202. doi:10.1007/s12144-013-9170-9
-Article type/purpose/theoretical orientation/research questions: This primary
research article is based on the theoretical orientation that personality is related to
genetic factors. Specifically, the authors investigated the relationship between
prenatal androgen exposure, as measured by 2D:4D, and the Big-Five personality
characteristics in men and women.
- Method: Participants included 71 female and 36 male university students. 2D:4D
measurements were obtained from photocopies of both hands. Participants completed
the NEO Five-Factor Personality Inventory, which measures the personality traits
neuroticism, extraversion, openness, agreeableness, and conscientiousness.
- Results: Overall, men had lower, more masculine, 2D:4D than women, and this
relationship was significant for the right hand. Women scored higher in neuroticism
than men. Men with higher, more feminine, right hand 2D:4D, and women with
higher left hand 2D:4D scored higher in openness, and this relationship was stronger
for men. All other personality traits were not correlated with 2D:4D.
-Limitations/strengths: A limitation of this study is that the authors reported that the
relationship between 2D:4D and openness for women was not significant, yet the pvalue for this relationship was .055. This is seemingly misleading. An additional
limitation was the use of a broad measure of openness. The authors report that women
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tend to be higher in emotional openness while men are more open to ideas.
Examining these specific subareas of openness may be beneficial to understanding
personality as it applies to men and women. A strength of this study is that it directly
measured the five personality traits and 2D:4D. The strength lies in the simplicity and
straightforwardness of the study design.
- Relevance: This study is relevant to my thesis because it examines the relationship
between 2D:4D, which is one of my study variables, and personality. Though
sociosexual orientation may not necessarily fall under personality, it may have
connections to 2D:4D. An additional aspect of this study that is relevant to my thesis
is the more highly significant relationship found for men regarding 2D:4D than the
relationship found for women and 2D:4D. While the relationship between openness
and 2D:4D for women was marginally significant, the relationship was much stronger
for men. This points to the possibility that 2D:4D is a better predictor of traits and
behaviors for men than for women. Because of this, I predict that relationships
between 2D:4D and my other study variables will likely be stronger for men than for
women.
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*Cecil, H., Bogart, L. M., Wagstaff, D. A., Pinkerton, S. D., & Abramson, P. R.
(2002). Classifying a person as a sexual partner: The impact of contextual
factors. Psychology and Health, 17, 221-234.
doi:10.108008870440290013699
-Article type/purpose/theoretical orientation/research questions: This primary
research article aims to provide a better understanding of the contexts under which
men and women define someone as a sexual partner. The authors hypothesized that
participants would unanimously agree that a man and woman (Tom and Lucy, the
hypothetical partners) were sexual partners if they had engaged in either vaginal or
anal intercourse, and were less likely to be labeled as sexual partners if they had only
engaged in oral sex. Additionally, it was hypothesized that Tom and Lucy would
more likely be defined as sexual partners if their relationship was described as longer
and if the sex act occurred frequently.
-Method: Participants included 145 women and 78 men between the ages of 19 and
40 years old. They completed a demographics questionnaire and read 16 scenarios
that depicted different contexts in which Tom and Lucy engaged in a sex act. The
contexts included: vaginal, anal, and oral intercourse; not dating, dated once, and
dated for three months; behavior performed once or several times. Participants read
each sexual behavior scenario and indicated whether Lucy would define the scenario
as sex and whether Tom would define the scenario as sex.
-Results: Overall, vaginal intercourse was the most likely to be considered sex,
followed by anal intercourse, then oral intercourse. Percentages were higher for Lucy
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than for Tom (i.e. Lucy was more likely to define an act as sex). The only sex act that
participants unanimously agreed was defined as sex was vaginal intercourse that
occurred several times over a three month relationship. The shorter the dating period
and the less frequent the sex act was, the less likely participants were to agree that
Tom or Lucy defined it as sex. There was no significant difference between men and
women’s responses. Lucy was more likely to label Tom as her sexual partner for
vaginal and oral sex, while there was no difference for anal sex.
-Limitations/Strengths: A strength of this study was the use of hypothetical scenarios.
Participants were likely more honest when classifying sex acts of hypothetical
characters as compared to classifying their own behaviors. A limitation of the study
was that participants were recruited from a human sexuality course at an American
university. Their responses may be different than the general population. For
example, it may be likely that people who take a human sexuality course are more
open to discussing sexuality and thus may respond to sex questionnaires in a more
honest or liberal way. An additional limitation was that all of the scenarios involved a
man and woman. Therefore, the study provides no further information regarding sex
acts for gay men, lesbians, and bisexuals.
- Relevance: This study is relevant to my thesis because it demonstrates the
importance of the definition of “sexual partner.” The behavior subscale of the SOI
measures the number of sexual partners in the past twelve months, and the number of
sexual partner with whom sex occurred one time only. Because these items are so
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vague, it is likely that participants over- or under-estimated their number of sexual
partners.
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Cheng, D., Hong, C.-J., Liao, D.-L., & Tsai, S.-J. (2006). Association study of
androgen receptor CAG repeat polymorphism and male violent criminal
activity. Psychoneuroendocrinology, 31, 548-552.
doi:10.1016/j.psyneuen.2005.11.004
-Article type/purpose/theoretical orientation/research questions: In this primary
research article, researchers hypothesized that violent male criminals would have
short CAG repeat lengths, as short repeats have been shown to be related to antisocial
and violent behaviors.
- Method: 146 violent male criminals serving time in a Chinese prison were recruited.
Any participant with a psychotic or mood disorder was excluded. An additional 108
non-criminal males were recruited from the community, also excluding anyone with
psychotic or mood disorders. Blood samples were collected to measure CAG repeat
length.
-Results: Although there were no significant differences in allele length between the
criminal and control group, there were more criminals with short CAG repeats. The
short repeat length cut-off for this study was 17 repeats which significantly correlated
to criminal activity. The shorter the repeat length, the younger the criminal was for
his first violent offence. However, somewhat contradictorily, researchers report that
androgen receptor sensitivity does not play a role in violent criminal activity.
-Limitations/strengths: This study is limited in that the researchers seem to disregard
their own findings. Based on the results, it seems as though short CAG repeat length
is related to male violent criminal activity, but the researchers report in the discussion
84
that there were no significant results. Also, the CAG repeat cut-off in this study was
17, which is lower than other studies I have read. Perhaps their results would have
been more significant had their cutoff been higher (only 11 criminal and 2 noncriminals fell under the short CAG repeat cutoff). Other studies have reported that
Asian men have the highest number of repeats among other races, so increasing the
cutoff would have been especially beneficial for this particular population. Also,
testosterone was not measured, which may interact with androgen sensitivity and
account for criminal behavior.
- Relevance: While it may not have the best analysis, this study is important because
it shows a relationship between CAG repeat length and behavior. This study has also
shown me that a very low cutoff to differentiate between short and long CAG length
may not be the most appropriate or accurate operational definition of repeat length.
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*Clark, A. P. (2004). Self-perceived attractiveness and masculinization predict
women's sociosexuality. Evolution and Human Behavior, 25, 113-124.
doi:10.1016/S1090-5138(03)00085-0
- Article type/purpose/theoretical orientation/research questions: This primary
research article consists of three studies. The first study aimed to examine the
relationship between women’s self-perceived attractiveness and sociosexual
orientation. The second study was similar to the first study, but 2D:4D measurements
were added. It was predicted that women with low 2D:4D measurements would score
as unrestricted. The third study added a spatial rotation task as a measure of
masculinity. It was hypothesized that spatial rotation, 2D:4D, and SOI would be
correlated.
- Methods study one: Participants included 37 Canadian women between the ages of
18 and 30 years old. They were presented with 20 pictures of women and rated each
woman as either more or less attractive than themselves in order to determine selfperceived attractiveness. Participants then completed the original unrevised SOI.
-Methods study two: Thirty-six Canadian women between the ages of 18 and 27
completed the task described in the first study. Their hands were then photographed
for 2D:4D measurements and their faces were photographed for third-party ratings of
attractiveness.
- Methods study three: Seventy-five Canadian women between the ages of 17 and 24
completed the tasks described in the second study followed by a spatial rotation task.
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Additionally, participants indicated whether or not they used hormonal contraceptives
and provided information about monthly purchases.
- Results: For study one, SOI scores and self-perceived attractiveness were positively
correlated. In contrast, there was no relationship between SOI scores and selfperceived or third-party perceived attractiveness in study two. However, right hand,
but not left hand, 2D:4D was negatively correlated with SOI scores. In study three,
there was no relationship between spatial rotation ability and 2D:4D measurements.
Women taking hormonal contraceptives scored higher on both SOI and the spatial
rotation task and rated themselves higher on attractiveness. SOI and self-perceived
attractiveness were positively correlated. Since third-party ratings of attractiveness
were not related to SOI or self-perceived attractiveness, the authors suggest that being
sexually unrestricted causes higher self-perceived attractiveness. SOI scores were
positively correlated with monthly alcohol purchases.
- Strengths/Limitations: A limitation of the study is that there were different rating
procedures for third-party raters versus self-perceived ratings in studies two and three.
This may be why the ratings did not agree. It is possible that ratings of full body
pictures of the participants may have better correlated with SOI scores since waist-tohip ratio would be considered. An additional limitation is that the researchers used the
unrevised version of the SOI and therefore did not analyze the three subscales of
sociosexual orientation. A strength of these studies is that each study progressively
improved with the addition of important variables, especially 2D:4D measurements.
87
- Relevance: This article is relevant to my thesis because it shows a negative
relationship between 2D:4D and SOI scores, which supports my hypothesis that
participants with lower 2D:4D ratios will scores as sociosexually unrestricted and
participants with higher 2D:4D ratios will score as sociosexually restricted.
88
Cleveland, E. S. (2014). Digit ratio, emotional intelligence and parenting styles
predict female aggression. Personality and Individual Differences, 58, 9-14.
- Article type/purpose/theoretical orientation/research questions: Many studies have
failed to find a relationship between females and aggression and the author of the
current primary research article believes this is due to the exclusion of female-typical
forms of aggression, such as social aggression. She predicted that social aggression
would be negatively correlated with 2D:4D measurements and emotional intelligence.
-Method: The sample was ethnically diverse and included 215 females with a mean
age of 20 years old. Participants completed five measures of aggression (Indirect
Aggression Scale, Direct and Indirect Aggression Scale, Self-Report of Aggression &
Social Behavior Measure–Romantic Relational Aggression, Driving Anger
Expression Inventory, and Social Responsibility on the Internet), a measure of
emotional intelligence (Trait Emotional Intelligence Questionnaire-Adolescent Short
Form), and two measures of parenting style (Perceptions of Parents Scales, and The
Parental Authority Questionnaire). 2D:4D was measured live and via scanned copies.
Participants also completed a gender identity questionnaire, demographics
questionnaire, and provided information regarding their current menstrual phase.
- Results: Aggression positively correlated with left hand, but not right hand, live
2D:4D measurements. Emotional intelligence negatively correlated with aggression.
Aggression positively correlated with authoritarianism.
- Strengths/Limitations: A strength of this study was the use of multiple measures of
aggression that better describe female forms of aggression. Most studies focus on
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overt aggression, which has only been found to be correlated to 2D:4D in males. A
limitation of this study is that the researcher did not investigate the effect of ethnicity
on 2D:4D, emotional intelligence, and parenting styles. It is likely that the variables,
most notably parenting style, may be affected by cultural differences.
- Relevance: This study found a positive relationship between aggression and 2D:4D,
which is in the opposite predicted direction. Perhaps indirect forms of aggression are
not influenced by androgens, while direct and overt forms of aggression are. Since
females are likely to compete in indirectly aggressive ways, based on this study, I
would predict that female participants with higher 2D:4D in my sample would be
more likely to fixate on models they deem to be their competition and rate models
higher in competition.
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Crabbe, P., Bogaert, V., De Bacquer, D., Goemaere, S., Zmierczak, H., & Kaufman,
J. M. (2007). Part of the interindividual variation in serum testosterone levels
in healthy men reflects differences in androgen sensitivity and feedback set
point: Contribution of the androgen receptor polyglutamine tract
polymorphism. The Journal of Clinical Endocrinology & Metabolism, 92,
3604-3610. doi:10.1210/jc.2007-0117
- Type of article/purpose/research questions: The objective of this primary research
was to examine the role of CAG repeat length in the variation of testosterone levels
and to determine the relationship between testosterone and leuteinizing hormone. A
positive relationship between testosterone and CAG repeat length as well as between
testosterone and LH was predicted.
- Method: Data were analyzed from two previous studies. Participants consisted of
2,322 men between the ages of 35 and 59 years old from the Belstress project, and a
separate sample of 358 men between the ages of 25 and 45 years old from the Siblos
study. Serum levels of testosterone, leuteinizing hormone, estradiol, and SHBG were
collected. Blood was collected to measure CAG repeat length.
- Results: Both samples presented a positive relationship between testosterone and
LH, as well as a positive relationship between testosterone and CAG repeat length.
The authors suggest the higher levels of testosterone that are related to longer CAG
repeats may reflect overcompensation for a less sensitive androgen receptor.
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- Limitations/strengths: Researchers state that the one-time hormonal assessment was
a limitation. However, the large sample size and the consistency of time of data
collection are strengths of the study.
-Relevance: This article pertains to my thesis because it examined the relationship
between CAG repeat length and testosterone. Most importantly, it suggested a reason
for the positive relationship (overcompensation of testosterone due to less sensitive
androgen receptor), which helps me better understand the biology and mechanisms of
the androgen receptor and its related gene.
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Csathó, Á., Osváth, A., Bicsák, É., Karádi, K., Manning, J., & Kállai, J. (2003). Sex
role identity related to the ratio of second to fourth digit length in women.
Biological Psychology, 62, 147-156. doi:10.1016/S0301-0511(02)00127-8
- Article type/purpose/theoretical orientation/research questions: This primary
research article aimed to examine the relationship between 2D:4D ratio and sex-role
identity in women. It was predicted that women with lower 2D:4D ratios would show
more masculine characteristics based on the Bem Sex-Role Inventory (BSRI), a selfreport measure of sex-role identity.
- Methods: Participants were recruited from University of Pѐcs in Hungary and
included 46 right handed females between the ages of 19 and 26 years old. 2D:4D
ratios were measured twice for each hand using a Vernier caliper. Participants then
completed the BSRI, which contains 20 masculine adjectives, 20 feminine adjectives,
and 20 gender neutral adjectives that are rated on a 7-point Likert scale to indicate
how well each word describes the participant.
- Results: After obtaining a t score for the difference between masculinity and
femininity scores, researchers performed a linear regression and found a negative
correlation between BSRI scores and right-hand 2D:4D and mean 2D:4D.
Participants who scored high on masculinity had lower right hand and mean 2D:4D
ratios, and those who scored high on femininity had higher right hand and mean
2D:4D ratios.
- Strengths/Limitations: A strength of this study is that it is one of the few that
examines 2D:4D and sex-role identity in women. However, the study may be limited
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by the sex-role identity measure, which has undergone criticism in the literature. It is
unclear whether participants are honestly self-reporting or if there is a high amount of
self-report bias. Future research should investigate multiple measures of sex-role
identity.
- Relevance: This article relates to my thesis because I will also investigate women’s
2D:4D ratios. Though I will not directly measure sex-role identity, I will utilize a
somewhat indirect measure of competition, which is thought to be a more masculine
characteristic. Based on the findings of this study, I would expect women with lower
2D:4D ratios to exhibit more competitive eye-gaze behavior, such as attending longer
and more often to the models they find to be their biggest competition.
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*Edelstein, R. S., Chopik, W. J., & Kean, E. L. (2011). Sociosexuality moderates the
association between testosterone and relationship status in men and women.
Hormones and Behavior, 60, 248-255. doi:10.1016/j.yhbeh.2011.05.007
- Article type/purpose/theoretical orientation/research questions: This primary
research article is based on Penke and Asendorpf’s multi-level measurement of
sociosexuality. The authors predicted lower testosterone levels in individuals in a
relationship versus those who were single.
They also predicted that women’s scores of behavior and men’s scores of
desire would positively correlate with testosterone levels, and that the partnered
individuals who scored as unrestricted in these areas would have testosterone levels
that were similar to single individuals. The authors predicted no associations with the
attitude subscale.
- Method: 135 male and 125 female Caucasian, African-American, Asian American,
and mixed ethnicity undergraduate students participated. Saliva samples were
collected to measure testosterone levels. Participants completed a demographics
questionnaire and the Sociosexual Orientation Inventory (SOI-R).
- Results: Men’s testosterone levels were significantly higher than women’s. Single
participants had higher levels of testosterone than partnered participants. This
relationship was significant for men, but not for women. Male testosterone levels
were positively correlated with desire and attitudes. Partnered participants scored
higher on the behavior subscale, but partnered women scored lower on the desire
subscale. Desire was positively associated with testosterone in partnered, but not
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single, men. Consistent with the hypothesis, women who scored high on the behavior
subscale had higher levels of testosterone.
- Strengths/weaknesses: A strength of this study is that it assessed the three
components of sociosexuality, instead of assessing the global scale. Additionally,
unlike most past research, women were examined. A limitation of this study is that it
does not show causality. We do not know if testosterone levels affect sociosexual
orientation or if the social environment changes testosterone levels. The authors state
the addition of participants’ perceived attractiveness would strengthen the study, as
attractiveness may explain partnered status. An additional limitation was the lack of
options for partnered status. The questionnaire did not distinguish between casual and
long-term relationships, nor did it assess relationship duration or sexual orientation.
- Relevance: This study is relevant to my thesis because it examines the relationship
between testosterone and sociosexuality. Though I am not measuring testosterone
levels directly, 2D:4D measurements may show similar relationships to SOI scores.
Based on the findings of this study, I would predict that men who score highly on
attitude and desire and women who score highly on behavior would have low 2D:4D
ratios.
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Elaut, E., Buysse, A., De Sutter, P., De Cuypere, G., Gerris, J., Deschepper, E., &
T’Sjoen, G. (2012). Relation of androgen receptor sensitivity and mood to
sexual desire in hormonal contraceptive users. Contraception, 85, 470-479.
doi:10.1016/j.contraception.2011.10.007
- Article type/purpose/theoretical orientation/research questions: This primary
research article aimed to investigate the influence of contraceptives and the androgen
receptor polymorphism on women’s testosterone levels, and if these factors had an
effect on sexual desire. The theoretical orientation of this study was that for women
fewer CAG repeats are associated with higher levels of androgens, and more CAG
repeats are associated with stronger receptor activity.
- Method: Participants included 55 heterosexual partners. The female participants
used three forms of contraceptives (combined oral contraceptive, progestin-only pill,
and vaginal ring) for three months each. Both partners filled out psychosexual
questionnaires (Sexual Desire Inventory, Maudsley Marital Questionnaire, Female
Sexual Function Index (women only), Symptom Checklist (SCL-90), and Rosenberg
Self-Esteem Scale) during the use of each contraceptive. Female blood samples were
taken throughout the study to measure serum levels of testosterone and CAG repeat
length.
- Results: Women with short CAG repeat lengths had higher serum testosterone levels
than women with long CAG repeat lengths. Women in the long repeat group showed
higher solitary and dyadic sexual desire. Solitary and dyadic sexual desire was
highest for women when they were using the vaginal ring. Solitary sexual desire was
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not affected by mood, but dyadic sexual desire was. Women’s baseline measure of
solitary and dyadic sexual desire best predicted their sexual desire in the study,
suggesting that sexual desire in women is a stable characteristic.
Women who used the vaginal ring at baseline maintained the highest levels of sexual
desire throughout the study. Dyadic sexual desire was positively correlated to the
women’s partner’s desire and being in a good mood.
- Limitations/strengths: This study is limited due to a small sample size. Also, not
every contraceptive held every possible position in the order (e.g. the progestin-only
pill was never the first contraceptive that a participant used). Another limitation to the
methodology was the lack of washout periods between contraceptives or a condomonly control. Finally, the population contained only young women, so the lengths of
their current relationships were not very long, and therefore the findings may not
relate to couples in much longer relationships. However, this study is important
because it took the effects of contraceptives into account, which many studies do not.
- Relevance: This study is relevant because it shows that women’s CAG repeat length
has an effect on their sexual desire, and thus may have an effect on participants’
responses on the SOI. Also, it suggests that it might be beneficial to include a
question about what kind of contraceptives our female participants use, since it may
affect their desire levels (although this may not be a change that can be made at this
point).
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Ellis, J. A., Stebbing, M., & Harrap, S. B. (2001). Polymorphism of the androgen
receptor gene is associated with male pattern baldness. The Society for
Investigative Dermatology, 116, 452-455.
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research article was to investigate the role of the androgen receptor in male
pattern baldness. The researchers operate on the theory that male pattern baldness is
caused by increased levels of DHT and sensitive androgen receptors.
- Method: 54 younger and 392 older men who exhibited balding and 107 older men
without balding were recruited from the Victorian Family Heart Study. Baldness was
determined via the Hamilton scale. CAG and GGC repeat length was determined as
high or low, depending on which side of the median (21 in this case) the repeats fell.
-Results: Young bald men were more likely to have short CAG repeat lengths as
compared to their non-bald counterparts. In general, the bald men had fewer CAG
repeats than the control group.
- Limitations/strengths: The authors state that in order for male pattern baldness to
manifest, both androgen receptor sensitivity and high levels of androgens need to be
present. However, they did not examine testosterone or DHT levels, only CAG and
GGC repeat lengths. The study is limited because it does not evaluate all of the
aspects required for the phenotype of male pattern baldness. It is also limited because
baldness may manifest later in life and the younger controls may actually have the
genotypic and phenotypic predisposition for baldness. A strength of this study is that
it examined a broad age range, including young men that exhibited male pattern
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baldness. Baldness in young men is likely due to androgens, whereas baldness in
older men may be a result of aging. Therefore, the inclusion of young men was
beneficial for this particular study.
- Relevance: Though androgen levels were not assessed, it is known that higher
androgen levels are necessary for male pattern baldness. In order for baldness to
manifest, there must be a combination of high androgen levels and high androgen
sensitivity (which in this study is operationalized as short CAG and GGC repeat
length). This shows that there is an interaction between androgen levels and the
androgen receptor and that one alone may not be responsible for physical effects.
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*Fink, B., Klappauf, D., Brewer, G., & Shackelford, T. K. (2013). Female physical
characteristics and intra-sexual competition in women. Personality and
Individual Differences, 58, 138-141. doi:10.1016/j.paid.2013.10.015
- Article type/purpose/theoretical orientation/research questions: This primary
research article investigated female competition and how it relates to physical
attractiveness. The authors predicted that the most attractive models (most feminine
facial characteristics, large breasts, and a low waist-to-hip ratio) would be rated by
female participants as the highest in competition.
- Method: Participants included 35 heterosexual German women ranging in age from
18-35 years old. They were told to imagine they were talking to a man they were
interested in when another woman began to flirt with him. The following stimuli
represented the “mate poacher”. Five pictures of a female face that ranged from very
masculine to very feminine were presented in random order, followed by five pictures
of a nude female torso ranging from small to large breasts in random order, and five
pictures of a nude female backside ranging from large to small waist-to-hip ratio in
random order. Participants then rated each picture based on threat from 1 to 5 (lowest
threat to highest threat) and femininity and attractiveness on a scale of 1 to 7 (not
attractive/feminine to very attractive/feminine).
- Results: Consistent with the hypothesis, more feminine faces, larger breasts, and
lower waist-to-hip ratios were found to be rated as the highest threat and rated as
more attractive and feminine.
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- Strengths/Limitations: A limitation of this study is that the external validity is low.
Though the participants were told to imagine they were at a party faced with this
competition (which increases the external validity), the pictures they viewed were
nude women. This does not accurately display the mating competition situation, since
women in the real world assess the threat of other women who are clothed. The breast
size and waist-to-hip ratio of the model could most likely be accurately assessed if the
model wore tight-fitting clothes. However, a strength of this study is that the stimuli
were altered images of one woman. This decreases the potential for confounds, such
as different skin tones or asymmetry associated with using multiple models. The
authors state that the smallest and largest breasts were rated as non threatening due to
perceived weights, but I believe it may be a function of the image morphing (the
“extremes” of each category seemed a bit unnatural).
- Relevance: This article is very relevant to my thesis because it implements a similar
methodology and examines competition. My study may be a more accurate
representation of a competitive mating situation since both male and female models
are included and all models are clothed.
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*Grimbos, T., Dawood, K., Burriss, R. P., Zucker, K. J., & Puts, D. A. (2010). Sexual
orientation and the second to fourth finger length ratio: A meta-analysis in
men and women. Behavioral Neuroscience, 124, 278-287.
doi:10.1037/a0018764
- Article type/purpose/theoretical orientation/research questions: This meta-analysis
aimed to clear up inconsistencies in the literature regarding the relationship between
2D:4D and sexual orientation.
- Methods: Twenty-one quantitative studies met the inclusion criteria for analysis
(must have investigated both homosexual and heterosexual participants and 2D:4D
must have been measured by a trained researcher). These studies included 16 samples
of women (1,693 heterosexual and 1,014 homosexual women) and 18 samples of men
(1,618 heterosexual and 1,503 homosexual men). The researchers conducted analyses
of 2D:4D between heterosexual and homosexual men, 2D:4D between heterosexual
and homosexual women, and 2D:4D between heterosexual men and women.
- Results: Heterosexual males had significantly lower 2D:4D ratios than heterosexual
females and this finding was most significant for the right hand. Homosexual women
had significantly lower 2D:4D ratios than heterosexual women. There was no
significant difference in 2D:4D ratios between homosexual and heterosexual men.
Geographic location was found to be a moderator for men such that European
homosexual men had lower 2D:4D ratios than their heterosexual counterparts and
North American homosexual men had higher 2D:4D ratios than their heterosexual
counterparts. Additionally, predominantly white samples showed lower 2D:4D ratios
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for homosexual men while samples with fewer white participants showed higher
2D:4D ratios for homosexual men. Further analyses showed that ethnicity, and not
geographic location alone, affected 2D:4D ratios.
- Strengths/Limitations: A strength of this article is that it was a meta-analysis that
helped clear up (to an extent) inconsistencies in the literature. The inclusion criterion
of 2D:4D measurement methods was also a strength. A limitation of many 2D:4D
studies is the use of self-reported 2D:4D measurements which are often inaccurate, so
excluding these studies strengthened the meta-analysis. A limitation of the metaanalysis is that it did not include unpublished studies that may have shown
insignificant results. The inclusion of such studies (though not plausible) may have
yielded alternate results.
- Relevance: This article is relevant to my thesis because it summarized the findings
regarding 2D:4D measurements and sexual orientation. While it is not one of my
research questions, I will be collecting data on both of these variables. Based on the
findings of the meta-analysis, I would predict lower 2D:4D ratios in homosexual
women compared to heterosexual women. Due to the insignificant differences
between homosexual and heterosexual men, I would not have a clear prediction
regarding 2D:4D and men’s sexual orientation.
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Hall, L. S., & Love, C. T. (2003). Finger-length ratios in female monozygotic twins
discordant for sexual orientation. Archives of Sexual Behavior, 32, 23-28.
doi:10.1023/A:1021837211630
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research was to investigate 2D:4D ratios in monozygotic female twins with
discordant sexual orientations. Previous research suggests that homosexual women
have lower, more masculine, 2D:4D, but this relationship has not been examined
among twins. The researchers hypothesized that homosexual women would have
lower, more masculine, 2D:4D ratios than their heterosexual twin.
- Methods: Participants were women between the ages of 25-56 and included seven
sets of monozygotic twins with discordant sexual orientations, and five sets of
monozygotic twins with concordant sexual orientations. The study consisted of an inperson interview. The Kinsey Scale and the Kline Grid were used to assess sexual
orientation and a blood test and questionnaire was used to assess zygosity. An ink
handprint was taken for each participant, which was later measured for 2D:4D.
Finger measurements from handprints have been found to be longer than finger
measurements from photocopies; however, the proportions remain the same.
- Results: Sexually discordant twins had significantly different 2D:4D ratios for both
hands, while sexually concordant twins did not differ in 2D:4D ratios for either hand.
Homosexual twins had lower 2D:4D ratios that were consistent with the average for
men, whereas heterosexual twins had higher 2D:4D ratios that were consistent with
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the average for women. Though not mentioned in the methods, male twins were also
assessed and no differences in 2D:4D were found.
- Strengths/Limitations: A strength of this study is its sample. Previous studies
examining sexual orientation and 2D:4D have only included unrelated individuals.
The authors state that by examining monozygotic discordant twins, they have
provided more thorough explanation that sexual orientation may be influenced by
differing androgen levels in the prenatal environment. However, a limitation of this
study is the extremely small sample size. There were only 24 participants to begin
with, which then became 20 when two sets of twins were excluded due to being
different ethnicities than the majority of the participants. Additionally, I feel that
authors did not do an adequate job of explaining how the prenatal environment could
differ for twins. I felt that more information was needed.
- Relevance: This article is relevant to my thesis because it examines 2D:4D ratios,
and I aim to add to the understanding of 2D:4D ratios. Though I am not directly
assessing the 2D:4D differences between homosexual and heterosexual people , this
article provides evidence that 2D:4D may be linked to prenatal environment and
androgen levels.
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Hampson, E., & Sankar, J. S. (2012). Re-examining the Manning hypothesis:
Androgen receptor polymorphism and the 2D:4D digit ratio. Evolution and
Human Behavior, 33, 557-561. doi:10.1016/j.evolhumbehav.2012.02.003
- Article type/purpose/theoretical orientation/research questions: This primary
research article aimed to replicate Manning’s (1998) finding that 2D:4D and CAG
repeat length are positively correlated. The authors state that Manning’s study was
flawed due to a very small sample size, so the current study examines the same
variables but with a larger sample.
- Method: Participants included 152 predominantly white males with a mean age of
18.7 years old. CAG repeat information and salivary testosterone were collected via
saliva sample. Two salivary testosterone samples were collected an hour and a half
apart. 2D:4D was measured via photocopies of the right and left hand.
- Results: There were no significant differences in 2D:4D for white and Asian
participants. No correlation was found between CAG repeat length and any measure
of 2D:4D (right, left, or the difference between right and left). CAG repeat length and
testosterone levels were not correlated.
- Strengths/Limitations: A strength of this study is that it questioned the
inconsistencies in the literature regarding the relationship between CAG repeat length
and 2D:4D. Specifically, it aimed to replicate Manning’s finding that CAG repeat
length and 2D:4D are positively correlated and used a larger sample size. However,
the sample size is not big enough to claim that beyond a doubt there is no relationship
between CAG repeat length and 2D:4D. A limitation of this study was the apparent
107
lack of objectivity. The authors provided no limitations to their methodology or
analysis.
- Relevance: This study is relevant to my thesis because I am basing my hypotheses
about the role of 2D:4D on Manning’s findings that 2D:4D and CAG repeat length
are positively correlated. This finding adds strength to 2D:4D since it correlates with
a measure of androgen sensitivity. Unfortunately, the current study found no such
relationship. This further adds to the inconsistencies in the literature which I aim to
address in my thesis.
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*Hampson, E., van Anders, S. M., & Mullin, L. I. (2006). A female advantage in the
recognition of emotional facial expressions: Test of an evolutionary
hypothesis. Evolution and Human Behavior, 27, 401-416.
doi:10.1016/j.evolhumbehav.2006.05.002
- Article type/purpose/theoretical orientation/research questions: This primary
research article is based on the child-rearing hypothesis that women are better attuned
to reading facial expressions for attachment promotion or threat detection.
Researchers examined if females were superior to males in recognizing emotional
facial expressions (attachment promotion hypothesis) and if females recognized
negative emotional facial expressions better than positive emotional facial
expressions (fitness threat hypothesis).
- Method: Thirty-one males and 31 females with a mean age of 20.8 years old
participated in the study. After completing a visual acuity test and demographics
questionnaire, participants completed control tasks (Verbal Meaning Test, and
Identical Pictures Test). The participants then completed the experimental task which
consisted of viewing pictures of faces on a computer one by one as quickly as
possible then pointing to a face on a spreadsheet that corresponded to it, which was
recorded by a research assistant. There were four randomized conditions in this
repeated measures design: facial matching (matching a neutral face on the computer
to the identical face and expression on the spreadsheet), facial identity (matching an
emotional facial expression to a picture of the same model with a neutral expression
on the spreadsheet), facial emotion (matching an emotional facial expression to the
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same emotional facial expression but with a different model on the spreadsheet), and
pattern matching (matching a shape to an identical shape on the spreadsheet).
Response time (RT) and accuracy were measured by the research assistant.
- Results: Both males and females were extremely accurate for all four experimental
conditions. The only emotions that did not reach a ceiling effect for accuracy were
disgust and anger, which showed a female advantage. There was no observed sex
difference for response times or accuracy in the facial matching, facial identity, and
pattern matching conditions, but there was a significant sex difference for the facial
emotion condition. Consistent with the attachment promotion hypothesis, females
showed a significantly quicker response time for identifying neutral facial
expressions, sadness, disgust, anger, and fear.
- Strengths/Limitations: A strength of this study is that it distinguished between
overall perceptual ability and emotional perceptual ability by examining four different
conditions. This helped to show that women were superior at interpreting emotional
facial expressions specifically and not that women were better at identifying people,
shapes, or identical pictures of faces. A possible limitation is that the researchers were
not able to discriminate between a female advantage or a male disadvantage. It is
clear that women were faster at identifying emotions, but it is not clear why. Though
their findings support the attachment promotion and fitness threat hypotheses for
women, there may be an additional theory that supports a slow response time for men.
Additionally, to truly test the attachment and child-rearing hypotheses, the researchers
should have used pictures of infants and children instead of adults.
110
- Relevance: This study is relevant to my thesis because it shows a sex difference in
response time while viewing emotional facial expressions, both positive and negative.
My study only portrays positive emotions, which women may recognize more
quickly. Because of this, I predict that women will not need to fixate on faces for very
long and will thus be more likely to look at clothing and background.
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*Hassebrauck, M. (1998). The visual process method: A new method to study
physical attractiveness. Evolution and Human Behavior, 19, 111-123.
doi:10.1016/S1090-5138(98)00002-6
- Article type/purpose/theoretical orientation/research questions: For this primary
research article, the author developed the Visual Process Method (VPM) to help
answer the following research questions: which facial and body features are required
to make judgments of physical attractiveness, and is there a gender difference in
terms of methods of seeking out physical attractiveness information? It was
hypothesized that for female targets, participants would seek visual information that
indicates sexual maturity and youthfulness, whereas features that indicate dominance
and masculinity would be sought for male targets.
- Method: Participants included 44 women and 26 men with a mean age of 23.01
years from a German university. Participants were presented with an outline of a
male or female body and instructed to assess the physical attractiveness of the target
with as few steps as possible. Typing a corresponding key would reveal a body part
or facial feature that the participant deemed necessary to see to judge physical
attractiveness. Participants were instructed to make a judgment after each portion
was revealed. They could reveal portions of the picture until all had been revealed or
until they felt they had enough information to accurately judge the physical
attractiveness of the model. The entre model was revealed and participants rated each
picture on a scale of 1 (very unattractive) to 9 (very attractive) and they’re response
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time was recorded. Pictures were taken outside by a pool and models (ten men and
ten women) wore bathing suits.
- Results: Internal consistency of ratings of attractiveness for male and female models
was extremely high for both men and women. Men required more portions to be
revealed than women in order to make a confident attractiveness judgment. An
interaction was revealed, such that men revealed more portions for female targets
than male targets, while women showed no significant difference in portion reveals
for male or female models. Men made attractiveness judgments about female models
significantly quicker than women made judgments about male models. Men also
processed attractiveness information faster than women for both and female models.
Women processed attractiveness faster for male models than female models. Eyes,
mouth, hair, and upper body were viewed the most, respectively, for both men and
women. For female targets, the eyes, mouth, and hip area were viewed the most,
which are thought to signify youth and fertility.
- Strengths/Limitations: A strength of this study is that utilized an original and clever
method of measuring attraction. The results reveal the different viewing strategies
that men and women use when trying to assess attractiveness, which would not have
been found had an eye tracker been used. A limitation of the study is that participants
did not know whether they were revealing portions of male or female models. The
order of reveals may have been different if the participants knew if they were about to
see a man or women.
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- Relevance: This study is relevant to my thesis because it provides an alternate
explanation as to why men’s fixation times on male and female models did not differ.
According to this study, men require less time than women to make attractiveness
judgments, and this may be why men in my sample did not fixate on female models
as long as expected.
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*Hewig, J., Trippe, R. H., Hecht, H., Straube, T., & Miltner, W. H. R. Gender
differences for specific body regions when looking at men and women.
(2008). Journal of Nonverbal Behavior, 32, 67-78. doi: 10.1007/s10919-0070043-5
- Article type/purpose/theoretical orientation/research questions: This primary
research article aimed to examine sex differences in gazing behavior while viewing
pictures of clothed men and women. It was predicted that faces would be viewed first
and for the longest time, and men would fixate on the breast region more than
women.
- Method: Participants included 14 female and 13 males, between the ages of 19 and
37 years old. While using an eye-tracker, participants were presented with 66
pictures, which included 15 front views of clothed male models and 15 front views of
clothed female models. The remaining pictures consisted of 12 positive, 12 neutral,
and 12 negative nonhuman images. Eight body regions were assessed, including
face/head, shoulders, breast, waist, hips, legs, arms, and hands.
Each image was shown for 4 seconds with 5 seconds between each image. At
the end of the experiment, participants viewed the male and female pictures again and
rated them based on the valence, arousal, and attractiveness of each model. Finally,
participants completed a questionnaire that assessed their sexual preference.
- Results: Participants rated models of the opposite sex as more appealing; however,
they fixated on pictures of their own sex more frequently. The face region received
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the most frequent, longest, and earliest fixations, and participants fixated longer on
the face region of the opposite sex. Male participants looked at the breast region
earlier than female participants, and female participants looked at the leg region
earlier than male participants. Men fixated on male models’ waists and arms, perhaps
as a form of rivalry and social comparison.
-Strengths/limitations: A limitation of this study is that only young, attractive models
were used. Also, photos may not be representative of real world interactions. The
authors suggest that future research should include a same-sex rivalry questionnaire,
and ratings of specific body regions, as well as video interactions between opposite
sex individuals. A strength of this study is that it used clothed males and females as
stimuli, which is more representative of real world interactions than viewing pictures
of nude models.
- Relevance: This study utilizes similar aspects of my thesis, including the eyetracker, attention to body and face regions of both male and female models, and
gender differences in gaze. The authors suggested measuring rivalry, which I believe
my thesis essentially does by assessing competition.
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*Hill, S. E. (2007). Overestimation bias in mate competition. Evolution and Human
Behavior, 28, 118-123. doi:10.1016/evolhumbehav.2006.08.006
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research is to examine if men and women over- or under-estimate their samesex mating competition. Since overestimation of competition is more beneficial than
underestimation, it was hypothesized that men and women would overestimate the
desirability of their same-sex competition.
- Method: This study consisted to two phases. The first phase included 159
heterosexual women and 123 heterosexual men with a mean age of 19.09 years who
rated pictures of opposite sex individuals. The second phase included 103
heterosexual women and 105 heterosexual men with a mean age of 19.22 years who
rated pictures of same-sex individuals. The stimuli consisted of ten pictures of
college age men, and ten pictures of college age women sitting alone outside at a
table. Participants rated opposite sex pictures on attractiveness, desirability as a
sexual partner, and desirability as a long-term partner, as well as additional ratings of
extraversion, desirability as a friend, and political involvement. Participants rating
same-sex individuals competed the same ratings based on how they believed the
opposite sex would rate the models.
- Results: A mixed model ANOVA revealed that female models were rated as more
desirable and more extraverted than male models. However, male models were rated
higher in friendliness than female models. Men rated the male models higher in
desirability than women rated the same male models, revealing an overestimation of
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desirability for same-sex individuals for men. Similarly, women rated female models
higher in desirability than men rated the same female models.
- Strengths/Limitations: The design of the study was a strength. By comparing two
groups (those who rated the same sex, and those who rated the opposite sex), the
researchers were able to conclude that individuals rated their competition higher in
desirability than potential mates (i.e. the opposite sex) rated the same models. A
limitation was the small number of ratings that do not encompass the gamut of mating
effort. In the future, researchers should include ratings of dominance, status,
resources, and characteristics associated with successful relationships.
- Relevance: This article is relevant to my study because, like my thesis, it examines
attractiveness and (indirectly) competition of same and opposite sex individuals.
Because men (and women) tend to overestimate the desirability of their competition,
it likely that the men in my study were threatened by the male models and thus
fixated on them longer than they fixated on the female models.
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*Hone, L. E., & McCullough, M. E. (2012). 2D:4D ratios predict hand grip strength
(but not hand grip endurance) in men (but not in women). Evolution and
Human Behavior, 33, 780-789. doi:10.1016/j.evolhumbehav.2012.07.003
- Article type/purpose/theoretical orientation/research questions: Past research shows
that 2D:4D may be related to physical prowess. The purpose of this primary research
was to examine if 2D:4D predicted endurance as well as strength, and if these
relationships were found for both me and women.
- Method: Participants included 100 men between the ages of 18 and 22 years old,
and 122 women between the ages of 17 and 48 years old from a university in Miami.
In order to complete the muscular voluntary contraction (MVC) task, participants sat
down with their arms on a table in front of them, held the dynamometer with their
dominant hand, and squeezed the dynamometer with their dominant hand. To
measure maximum endurance time (MET), participants repeated the procedure above,
but only gripped strongly enough to reach 70% of their MVC. Researchers began
timing when grip strength reached 70% and stopped timing when measurements fell
below 70%. The MET procedure was repeated and participants filled out a
demographics questionnaire. 2D:4D measurements were obtained from photocopies
of the dominant hand.
- Results: Men had significantly lower 2D:4D ratios than women. Men had higher
scores on MVC and MET as compared to women. MVC and MET scores were not
correlated. 2D:4D significantly predicted MVC for men, but not women. The
interaction between sex and 2D:4D, and 2D:4D alone, did not predict MET.
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- Strengths/Limitations: A strength of this study is that it expanded upon past
research that suggests 2D:4D is negatively associated with physical prowess (lower,
more masculine, 2D:4D is associated with more physical prowess). The authors
discovered that strength, but not muscular endurance, is associated with 2D:4D. An
additional strength is that height, weight, and age were controlled for in analysis. A
limitation of the study is that participants did not have much time to rest between the
MVC and MET tests, and therefore, endurance (MET) may have been
underestimated.
- Relevance: This study is relevant to my thesis because it demonstrates a sex
difference in 2D:4D. Additionally, it provides evidence that 2D:4D may be related to
competition in men, since strength is evolutionarily thought to be an advantage in
competition.
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*Hönekopp, J. (2011). Relationships between digit ratio 2D:4D and self-reported
aggression and risk taking in an online study. Personality and Individual
Differences, 51, 77-80. doi:10.1016/j.paid.2011.03.010
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research was to examine the relationship between 2D:4D and aggression and
risk taking in men and women. Previous research is inconclusive regarding the role
2D:4D plays in aggression, and lower, more masculine, 2D:4D is associated with risk
taking behaviors.
- Method: Participants were recruited from a German science television program and
included 1038 women and 1254 men with a mean age of 35.3 years. The study was
then completed online. Participants were instructed to measure their own 2D:4D
using a ruler and rounding to the nearest millimeter. They then completed the verbal
(five items) and physical (nine items) aggression portions of the Buss and Perry
aggression questionnaire and an additional ten questions that measured risk taking.
- Results: Initial analysis of 2D:4D measurements revealed outliers (likely due to
inaccurate measurements) that were removed, and consisted of 1.5% of the sample.
Because the standard deviation between measurements was higher than what is
normally found using expert measurements, the authors suggest that selfmeasurements may not be accurate. For men, left hand 2D:4D and verbal aggression
were negatively correlated. For women, right hand 2D:4D was negatively associated
with risk taking. After a reliability reduction adjustment was made for 2D:4D
measurements, men’s 2D:4D was negatively associated with overall aggression.
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- Strengths/Weaknesses: A strength of this study was its large sample size, which is
the largest in this field of research. However, a limitation of this study was the use of
self-measured 2D:4D. Because of the unusually high variance in measurements, it is
likely that many measurements may be inaccurate. An additional weakness was the
lack of ethnic or sexual orientation information in the demographics questionnaire.
- Relevance: This study is relevant to my thesis because it shows a relationship
between one of my study variables—2D:4D—and aggression. Though aggression
and competition are not the same characteristic, they may be similar, and thus the
relationship between 2D:4D and competition may be similar to the relationship
between 2D:4D and aggression. Also, this study provides evidence that self-reported
2D:4D measurements may not be as accurate as expert measured 2D:4D.
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*Hönekopp, J., & Schuster, M. (2010). A meta-analysis on 2D:4D and athletic
prowess: Substantial relationships but neither hand out-predicts the other.
Personality and Individual Differences, 48, 4-10.
doi:10.1016/j.paid.2009.08.009
- Article type/purpose/theoretical orientation/research questions: The purpose of this
meta-analysis was to determine if right hand 2D:4D—which has been found to be the
more sexually dimorphic of the two hands—is indeed a better predictor of athletic
prowess than left hand 2D:4D. The authors chose to examine athletic prowess as the
outcome variable because previous research has shown a consistent negative
correlation between 2D:4D and athletic prowess. Additionally, the authors examined
if running ability was correlated with 2D:4D.
- Method: The authors meta-analyzed 24 right hand 2D:4D studies that totaled 2,810
participants, and 22 left hand 2D:4D studies that totaled 2,791 participants.
Demographic information was not provided. Studies were compared based on the
effect size, r, of the relationship between 2D:4D and the measure of athletic prowess
for each study.
- Results: Both right and left hand 2D:4D were significantly negatively correlated
with athletic prowess. Neither age nor sex moderated the relationship between
2D:4D and athletic prowess. However, running ability moderated the relationship
between 2D:4D and athletic prowess, such that those who could run for a longer
distance had lower 2D:4D. Neither hand was better than the other at predicting
athletic prowess.
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- Strengths/Limitations: A strength of this study was that it was a meta-analysis. By
combining the results of multiple studies, the authors were able to come to the
conclusion that there is a very strong relationship between 2D:4D and measures of
athletic prowess. An additional strength was the inclusion of studies that examined
both right and left hand 2D:4D so that the predictive power of athletic prowess could
be compared between hands. The authors did not specifically state what the measures
of athletic prowess were for each study. Therefore, no conclusions can be drawn
regarding what aspect of athleticism is specifically linked to 2D:4D (i.e. endurance,
oxygen intake, muscle mass, etc.).
- Relevance: This meta-analysis is relevant to my thesis because it identifies a strong
relationship between 2D:4D and a characteristic, in this case, athletic prowess.
Though I did not measure athletic prowess, it is important to identify that 2D:4D
correlates strongly and negatively with characteristics that are deemed masculine.
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*Honekopp, J., Voracek, M., & Manning, J. T. (2006). 2nd to 4th digit ratio (2D:4D)
and number of sex partners: Evidence for effects of prenatal testosterone in
men. Psychoneuroendocrinology, 31, 30-37.
doi:10.1016/j.psyneuen.2005.05.009
- Article type/purpose/theoretical orientation/research questions: In this primary
research article, the authors state that right hand 2D:4D is more strongly associated
with traits than left hand 2D:4D. They hypothesized that right hand 2D:4D would be
negatively associated with number of sexual partners for males.
- Method study one: Ninety-nine German Caucasian heterosexual men completed a
survey that assessed their lifetime number of sexual partners. 2D:4D was measured
via photographs, and blood samples were collected to measure serum testosterone
levels.
- Method study two: Seventy-nine heterosexual and 95 homosexual Caucasian
Austrian men provided information about their sexual orientation and number of
sexual partners in the past year, as well as their education level and work status
(white-collar or blue-collar). 2D:4D was measured via photocopies. There was no
measurement of free testosterone.
- Results: Study one showed a significant negative association between right hand
2D:4D and number of sexual partners. There was no significant correlation between
left hand 2D:4D and number of sexual partners. Free testosterone levels were
correlated to number of sexual partners; however, free testosterone levels and 2D:4D
measurements were not correlated. Study two showed that homosexual men had
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significantly more sexual partners than heterosexual men in the past year. Consistent
with study one, a significant negative correlation was found between right hand
2D:4D and number of sexual partners in heterosexual, but not homosexual, men. No
relationship was found for left hand 2D:4D. Years of education did not correlate to
2D:4D.
- Limitations/strengths: A limitation of these studies is that self-reported measures of
number of sexual partners may be inaccurate or exaggerated. Also, number of sexual
partners may be affected by the androgen receptor gene, and not just 2D:4D. Study
one seemed to be stronger than study two since there were two measurements of
androgens (2D:4D and serum testosterone). The population of study two was broader
(both heterosexual and homosexual men), but there was little explanation as to why
no relationship between 2D:4D and number of sexual partners was found for
homosexual men.
- Relevance: Number of sexual partners is related to the behavior subscale of the
Sociosexual Orientation Inventory, which I will examine in my thesis. Based on the
findings from this study, I would predict that the heterosexual males in my study who
score highly on the behavior subscale would have low 2D:4D ratios.
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*Hönekopp, J., & Watson, S. (2010). Meta-analysis of digit ratio 2D:4D shows
greater sex difference in the right hand. American Journal of Human Biology:
The Official Journal of the Human Biology Council, 22, 619-630.
doi:10.1002/ajhb.21054
- Article type/purpose/theoretical orientation/research questions: The purpose of this
meta-analysis was to examine gender differences in 2D:4D, and to examine the
reliability of 2D:4D self-measurements.
- Method: One hundred sixteen articles that provided information about right and left
hand 2D:4D for both men (n = 11,017) and women (n = 12,507) were meta-analyzed.
Random effects models were used to determine differences between right and left
hand 2D:4D and Cohen’s d was used as the measure of effect size for the differences.
Studies with larger sample sizes were given more weight. To analyze the loss in
reliability for self-measurements as compared to expert measurements, the relative
reliability of self-measurements was compared to the relative reliability of expert
measurements.
- Results: The revealed that the right hand is more sexually dimorphic (d = 0.457)
than the left (d = 0.376), with males having significantly lower right hand 2D:4D
ratios (M = 0.959) than females (M = 0.975). They suggest that the right hand may be
more sensitive to prenatal androgens, and thus a better representation of prenatal
androgen exposure than the left hand. In regards to the type of measurement, expert
measurements of 2D:4D have significantly less variability than self-measurements of
2D:4D.
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- Strengths/Limitations: This analysis is limited because it is likely that articles with
non-significant 2D:4D results were not published, and thus, not included. Therefore,
the results may not be entirely representative. A strength of this meta-analysis was
the use of multiple studies, which resulted in a comprehensive examination of sex
differences in 2D:4D that could not be as confidently concluded from one sample.
Also, by comparing the variability in self-measurements and expert measurements,
we now know that self-measurements may not be reliable enough to use in scientific
research.
- Relevance: This meta-analysis is relevant to my thesis because it shows that the
right hand is more sexually dimorphic, and thus, right hand 2D:4D may be a stronger
predictor of outcomes than left hand 2D:4D. Because of these findings, I predicted a
strong relationship between right hand 2D:4D and my study variables and a strong
sex difference in 2D:4D, however, that was not the case. This further solidifies my
assumption that the 2D:4D measurements obtained for my study were inaccurate, as
they did not reflect the conclusions of this meta-analysis.
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Huh, H. (2013). Digit ratios, but not facial width-to-height ratios, are associated with
the priority placed on attending to faces versus bodies. Personality and
Individual Differences, 54, 133-136. doi:10.1016/j.paid.2012.08.032
- Article type/purpose/theoretical orientation/research questions: This primary
research article examined the relationship between 2D:4D, facial width to height ratio
(WHR), and attention to either faces or bodies. It was predicted that low 2D:4D ratios
and high WHR would be associated with attention to bodies.
- Methods: Participants were 99 Korean college students, and included 64 men with a
mean age of 22.4 years old and 35 women with a mean age of 20.8 years old. They
were given a picture of a male or female celebrity (whichever was the opposite sex of
the participant) that had a box covering the head and a box covering the body.
Participants were allowed to remove one box, either revealing the celebrity’s head or
body. This procedure was videotaped and later coded by researchers. Participants’
face and right hand were then photographed and later measured to obtain 2D:4D and
WHR. Finally, participants completed a demographics questionnaire.
-Results: Men and women differed significantly in facial WHR (men had higher
WHR than women), but did not differ in 2D:4D ratios. There was a positive
correlation between 2D:4D and WHR for women, but not for men. Men and women
did not differ significantly in their choice of which box to remove. The participants
who chose to view the body had significantly lower 2D:4D ratios than those who
chose to view the face. There was no significant correlation between facial WHR and
the chosen box.
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- Strengths/Limitations: A strength of this study was the examination of both 2D:4D
and facial WHR. An additional strength was the ability to clearly differentiate
between the attention paid to either the face or body. However, this methodology
raises some ecological concerns. The external validity could be improved by utilizing
an eye-tracker to determine attention paid to the face and body. Also, the study may
have been limited by the lack of ethnic diversity. It has been found that Asian males
have higher 2D:4D ratios on average, and this may account for why no significant
difference was found between male and female 2D:4D ratios.
- Relevance: This article is relevant to my thesis because it shows a relationship
between 2D:4D and attention, two variables I will examine. The results agree with
my hypothesis that those with lower 2D:4D ratios will visually attend to bodies more
than those with higher 2D:4D ratios. Unlike this study, I will be utilizing an eyetracker, a more ecological measurement of visual attention.
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*Knickmeyer, R. C., Woolson, S., Hamer, R. M., Konneker, T., & Gilmore, J. H.
(2011). 2D:4D ratios in the first 2 years of life: Stability and relation to
testosterone exposure and sensitivity. Hormones and Behavior, 60, 256-263.
doi:10.1016/j.yhbeh.2011.05.009
- Article type/purpose/theoretical orientation/research questions: This primary
research article aimed to investigate if the neonatal surge of testosterone at three
months of age has an effect on 2D:4D measurements at two years old. This
longitudinal study examined 2D:4D measurements, circulating testosterone levels,
and CAG repeat length in babies when they were two weeks to two years old.
- Method: Participants were 364 babies between the ages of zero to two years old and
included 167 non-twin babies (86 females and 81 males) and 197 twins (97 females
and 100 males). 2D:4D measurements were made from photocopies of both hands at
two weeks old, 12 months old, and 24 months old. Salivary testosterone and buccal
cell samples were collected at three months old.
- Results: There was no difference in 2D:4D ratios between twins and non-twins.
African American participants had lower 2D:4D ratios than Caucasian participants
and this difference was most significant for the right hand at two weeks old. Males
had significantly lower 2D:4D than females at two weeks old and the trend continued,
though not significantly, at 12 and 24 months old. 2D:4D measurements varied with
age, the lowest measurement being observed at 12 months old. There was no
significant correlation between salivary testosterone and 2D:4D at any age, though
the trend was in the predicted direction of an inverse relationship. 2D:4D was not
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related to CAG repeat length. However, the interaction of testosterone and CAG
repeat length predicted male 2D:4D at 12 months for right and left hands and 24
months for left hand. No significant results were found for females regarding the
interaction between testosterone levels and CAG repeat length.
- Strengths/Limitations: A strength of this study is its novelty. Very few, if any,
studies have examined 2D:4D in very young children. An additional strength was the
examination of circulating testosterone levels and CAG repeat length. A limitation
was the single sample of salivary testosterone at three months old. Multiple samples
may have yielded a more precise measurement.
- Relevance: This study is relevant to my thesis because it examines the formation of
2D:4D ratios in infancy and shows that testosterone levels and CAG repeat length
interact to affect 2D:4D ratios in males. This study is important because it may show
that 2D:4D is not only affected by prenatal androgen exposure, but also by the
neonatal testosterone surge around three months of age.
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*Levy, B., Ariely, D., Mazar, N., Chi, W., Lukas, S., & Elman, I. (2008). Gender
differences in the motivational processing of facial beauty. Learning and
Motivation, 39, 136–145.
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research was to assess wanting and liking of opposite sex models by
measuring the amount of time participants chose to view a picture (wanting) and
attractiveness ratings (liking). The researchers hypothesized that women would rate
men and women as equally attractive, but view the pictures for a shorter amount of
time than men. Whereas men were predicted to rate women as more attractive than
men, and spend a longer amount of time viewing pictures of women.
- Method: The sample consisted of 18 male and 17 female heterosexual college
students who were presented with 80 pictures of average men and women, and
beautiful men and women, with 20 pictures in each of the four categories. Each
picture had a default presentation time of four seconds, but participants could either
increase or decrease the amount of time each picture appeared on the screen by
pressing certain keys on the keyboard. They then viewed each picture again and rated
it on a 100-point attractiveness scale.
- Results: The beautiful faces were rated higher in attractiveness than the average
faces and men rated male models significantly lower in attractiveness. There were no
significant differences between men and women’s ratings of beautiful women, nor
were there differences between men’s ratings of beautiful women compared to
women’s ratings of beautiful men. Men rated beautiful males significantly lower than
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women rated the same pictures. Men engaged in significantly more key presses than
women to increase the amount of time beautiful women appeared on the screen. Men
viewed female models for a longer amount of time than male models, whereas
women viewed male and female models for an equal amount of time.
- Strengths/Limitations: A strength of this study is that participants were in control of
the length of time they were able to view each picture. This method assesses
conscious decisions made by participants to view or not view a picture they want or
don’t want to look at. This differs from studies that measure fixation time on
pictures. A limitation of this study is that the authors posit that men may have a more
sensitive neurological system for identifying female beauty as compared to women.
However, if this were indeed the case, then it seems more likely that men would
spend a shorter amount of time processing female beauty if they were more sensitive
to it than women. Additional limitations to this study were the small sample size and
exclusion of homosexual participants.
- Relevance: This study is relevant to my thesis because it demonstrates that men
prefer to spend more time viewing female models compared to male models, while
women’s viewing times of male and female models do not differ. I expected similar
results with my sample.
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Loehlin, J. C., Spurdle, A., Treloar, S. A, & Martin, N. G. (1999). Number of Xlinked androgen receptor gene CAG repeats and femininity in women.
Personality and Individual Differences, 27, 887-899. doi:10.1016/S01918869(99)00038-0
- Article type/purpose/theoretical orientation/research questions: This article is
comprised of two primary research studies. The first investigated CAG repeat length
and psychological femininity in women and predicted that women with shorter CAG
repeat length (more sensitive androgen receptors) would score as more masculine.
The second study examined the role of CAG repeat length in female reproductive
traits.
- Method first study: Participants included 300 Australian female monozygotic twins
who were previously controls for an ovarian cancer study. Gene, personality, and
reproductive data were collected during the previous study. Items from the Eysenck
Personality Questionnaire and the Cloninger Tridimensional Personality
Questionnaire were combined to make three scales that included “worried”,
“reserved”, and “breaks rules.”
Method second study: The second study examined data from a previous study that
compared reproductive traits between same-sex and opposite-sex twins. The number
of participants varied per each of the 90 questions about reproduction (i.e.
menopause, contraception, child-birth, etc.).
Results: A non-significant positive relationship between CAG repeat length and
scores on the worry scale was found. A significant negative correlation between CAG
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repeat length and scores on the reserved scale was found, thus women with shorter
CAG repeats scored as masculine (reserved). For the second study, a negative
correlation was found between CAG repeat length and age, length of second childbirth, and hysterectomy. Though the authors do not understand why repeat length
would differ between ages, they suggest that it is possible that women with shorter
CAG repeats may live longer.
- Limitations/strengths: A limitation of the first study was the use of only self-report
measures. The authors suggest future research should incorporate peer or spouse
responses, and should include male participants. A strength of these studies is that the
authors used information from the second study to explain phenomena in the first
study. For example, worry and rule breaking decreased with age, while reservation
increased with age, suggesting that age may mediate the relationship between CAG
repeat length and masculinity. The second study was limited because the correlations
were weak and, for the most part, unexplainable. The authors caution against
reporting the second study findings as true.
- Relevance: This study is relevant to my thesis because it provides some support that
women with shorter CAG repeat lengths may behave in a more masculine way, at
least in terms of reservation. Though it is inconsistent with my current hypotheses,
this may mean that participants with shorter CAG repeats may be more reserved, and
thus less competitive.
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Lukaszewski, A. W., & Roney, J. R. (2011). The origins of extraversion: Joint effects
of facultative calibration and genetic polymorphism. Personality and Social
Psychology Bulletin, 37, 409-421. doi:10.1177/0146167210397209
- Article type/purpose/theoretical orientation/research questions: This article consists
of two primary research studies that theorized that attractiveness and physical
strength are necessary for reproductive success and may be related to extraversion.
The first study hypothesized that extraversion would correlate with attractiveness and
strength. The second study aimed to test the mediating effects of the androgen
receptor polymorphism on attractiveness and strength and it was hypothesized that
the polymorphism would play a role in extraversion.
- Method study one: Participants included 85 male and 89 female UC Santa Barbara
students. Extraversion, shyness, and social attention was measured via questionnaire
(i.e. IPIP HEXACO Extraversion). Attractiveness was based on self-ratings and grip
strength and arm/chest strength was measured with a dynamometer.
- Method study two: 146 men and 52 women from UC Santa Barbara participated in
the second study. Extraversion, self-rated and other-rated physical attractiveness, and
strength were measured. Only male participants were genotyped for CAG repeat
length and this was obtained via mouthwash samples. Because CAG repeat length
was positively skewed, analyses were based on a median split between short and long
CAG repeats (<22 or >22).
-Results: In study one, physical attractiveness was positively correlated with
extraversion in both men and women. Physical strength predicted extraversion in
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men. In study two, strength and physical attractiveness positively predicted
extraversion in men, while CAG repeat length negatively predicted it. In other words,
men with shorter CAG repeats were more likely to exhibit extraversion. Physical
attractiveness was positively correlated to extraversion in females. The findings
suggest that strength, attractiveness, and CAG repeat length all work independently of
one another to influence extraversion in men.
- Limitations/strengths: A limitation of the first study was the use of self-rated
attractiveness and not ratings from others. However, I feel that extraversion would
most likely be linked to how one feels about oneself, so this limitation is only a minor
weakness. Also, study two determined that self-rated attractiveness and other-rated
attractiveness were strongly correlated. The authors state another limitation of the
study is that it shows correlation, not cause. It may be that extraverted individuals
take more care in their appearance, or attractive children are more likely to become
extraverted. Also, women were not genotyped and thus there is no evidence for a
CAG repeat relationship with extraversion for women. Finally, extraversion was only
measured via self-report. A more naturalistic, behavioral, and/or observational
measurement may be more accurate.
- Relevance: Though I am not investigating extraversion, this study shows that CAG
repeat length may influence personality characteristics. The final limitation listed and
the advice for future research may actually be a strength of my study. Incorporating
the eye-tracker data with ratings may obtain more naturalistic results, as opposed to
self-reports alone.
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*Manning, J. T., Bundred, P. E., Newton, D. J., & Flanagan, B. F. (2004). The second
to fourth digit ratio and variation in the androgen receptor gene. Evolution and
Human Behavior, 24, 399-405. doi:10.1916/S1090-5138(03)00052-7
- Article type/purpose/theoretical orientation/research questions: This primary
research is based on the theory that testosterone sensitivity is determined by CAG
repeat length in the androgen receptor gene and lower numbers of repeats indicate
higher sensitivity to androgens. Since digit length is affected by prenatal androgen
exposure and CAG repeat length determines sensitivity to prenatal androgens, it was
predicted that 2D:4D and CAG repeat length should be positively correlated.
- Method: 50 men (M = 32.63) participated in the study. Second and fourth digits of
both hands were measured with a vernier caliper to obtain 2D:4D ratio and blood
samples were drawn to assess CAG repeat length.
- Results: A significant positive relationship was found between CAG repeat length
and right hand 2D:4D, but no relationship was found for left hand 2D:4D. The
difference between right and left hand 2D:4D was also positively correlated to CAG
repeat length. The authors report that digit ratio is likely determined by androgen
sensitivity (CAG repeat length), such that the more sensitive an androgen receptor is
(short CAG repeat length) the lower the digit ratio will be.
- Limitations/strengths: This study is limited because it only examined the
relationship of 2D:4D and CAG repeat length in white men. It does not help explain
how this relationship applies to women or different ethnicities. However, a strength of
this study is the use of multiple measurements of 2D:4D.
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- Relevance: Contrary to other findings, this study suggests right hand 2D:4D and the
difference between right and left hand 2D:4D are the most reliable measurements. I
will use this information to guide my decision making during analysis. I will examine
all four measurements of 2D:4D- right, left, average, and the difference between right
and left- to determine which is most appropriate for my analysis.
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*Manning, J. T., Scutt, D., Wilson, J., & Lewis-Jones, D. I. (1998). The ratio of 2nd to
4th digit length: A predictor of sperm numbers and concentrations of
testosterone, luteinizing hormone and oestrogen. Human Reproduction, 13,
3000-3004.
- Article type/purpose/theoretical orientation/research questions: This primary
research is based on the role of Hox genes in the formation of gonads,
spermatogenesis, and finger length. The researchers purposed that there is a sex
difference in finger length (i.e. 2D:4D) since the mechanism related to fertility (Hox
genes) also play a role in the development of finger length. It was predicted that men
would have lower, more masculine 2D:4D, whereas women would have higher, more
feminine, 2D:4D.
- Method: The first study comprised 400 female and 400 male participants between
the ages of two to 25 years old. Each age group consisted of 40 participants.
Researchers measured 2D:4D of both hands using a Vernier caliper and the first 100
participants’ hands were measured twice to ensure reliability. The second study
consisted of 69 men with a mean age of 34 years and 62 women with a mean age of
31 years. 2D:4D measurements were obtained for both hands twice following the
procedure previously described. Fifty-eight males provided semen samples, which
were analyzed sperm number, motility, and speed. Blood samples were obtained and
oestrogen, prolactin, LH, and FSH levels were measured for men (n = 58) and women
(n = 40) and testosterone levels were measured for males only.
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- Results: In study one, men had significantly lower 2D:4D than women. Age did not
moderate 2D:4D measurements. In study two, right hand 2D:4D was significantly
lower for men than women. Left hand 2D:4D was not significantly different for men
and women, though there was a similar trend. Twelve men who had no spermatozoa
had significantly higher, more feminine, right hand 2D:4D than the rest of the sperm
producing men in the sample. A similar, but non-significant trend was found for the
left hand. Number of spermatozoa and testosterone levels were significantly
negatively correlated with right hand 2D:4D. Right hand 2D:4D was significantly
positively correlated to prolactin, LH, and oestrogen levels in both men and women.
The authors suggest that since 2D:4D is, in part, determined by prenatal testosterone
levels, these levels in turn affect spermatogenesis in adulthood.
- Strengths/Limitations: Strengths of this study include the reliability checks of
2D:4D measurements, the inclusion of blood samples to test hormone levels, and the
wide age range in participants. A limitation of the study was that testosterone levels
were not also measured in women. Being that Hox genes interact with prenatal
androgen levels to develop finger length, it seems appropriate that testosterone levels
be measured later in life, including women.
- Relevance: This study is relevant because it is among the first of its kind and
provided the basis of our understanding of 2D:4D. It is relevant to my thesis because
it demonstrates that men have significantly lower 2D:4D than women and that this
relationship, among other correlates, are stronger for the right hand than the left hand.
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It is surprising that I did not find similar results for my study, and thus, it is likely that
the measurements obtained for my study were inaccurate.
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Manuck, S. B., Marsland, A. L., Flory, J. D., Gorka, A., Ferrell, R. E., & Hariri, A. R.
(2010). Salivary testosterone and a trinucleotide (CAG) length polymorphism
in the androgen receptor gene predict amygdala reactivity in men.
Psychoneuroendocrinology, 35, 94-104. doi:10.1016/j.psyneuen.2009.04.013
- Article type/purpose/theoretical orientation/research questions: This primary
research aimed to determine if CAG repeat length and testosterone levels are
predictive of men’s amygdala reactivity while viewing threatening faces.
- Method: Participants consisted of 41 European-American men between the ages of
34 and 54 years old who were recruited from the Adult Health and Behavior Project.
Blood and saliva samples were collected to measure CAG repeat length and
endogenous testosterone levels, respectively. Participants viewed three pictures of
faces for four seconds that expressed either fear or anger and had to match the two
identical faces out of three. They did this six total times. The control session consisted
of pictures of three shapes which participants matched. Each participant underwent
both conditions. fMRI data were collected and the brain regions of interest (ventral
and dorsal amygdala) were contrasted. Amygdala reactivity was defined as BOLD
contrast estimates of the ventral and dorsal amygdala regions, as recorded by fMRI.
- Results: Testosterone and CAG repeat length were positively correlated. There was
a negative correlation between CAG repeat length and activity of the ventral
amygdala, while testosterone levels correlated positively to ventral amygdala
reactivity. Researchers postulate that the positive relationship between CAG repeat
length and testosterone levels may be due to higher levels of leuteinizing hormone in
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those with less sensitive androgen receptors (higher number of CAG repeats).
However, they report that results remain inconsistent.
-Limitations/strengths: Limitations included only measuring testosterone levels once
and at a different time than fMRI data collection. Also, the study only examined
Caucasian men, limiting its generalization to other populations.
- Relevance: This article is relevant to my thesis because it provides information
regarding the relationship between testosterone and CAG repeat length (positive
relationship). This will help guide my hypotheses about CAG repeat length because
some behaviors that are suggested to be related to testosterone levels may also be
related to CAG repeat length. I will use this study as one piece of evidence of the
positive relationship between testosterone levels and CAG repeat length, though it
conflicts with the majority of other articles I have read.
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Medland, S. E., Duffy, D. L., Spurdle, A. B., Wright, M. J., Geffen, G. M.,
Montgomery, G. W., & Martin, N. G. (2005). Opposite effects of androgen
receptor CAG repeat length on increased risk of left-handedness in males and
females. Behavior Genetics, 35, 735-744. doi:10.1007/s10519-005-6187-3
- Article type/purpose/theoretical orientation/research questions: This meta-analysis
aimed to investigate if CAG repeat length mediated the effects of testosterone on lefthandedness. It was hypothesized that the correlation between CAG repeat length and
testosterone levels would be opposite for men and women.
- Method: Data were analyzed from three independent samples of same-sex twins
which consisted of 287 female and 128 male participants who had already been
genotyped for the androgen receptor in previous studies. Handedness was defined as
the hand used for writing. There were 47 left-handed females and 29 left-handed
males.
- Results: Left-handedness was more common among females with longer CAG
repeats. The inverse relationship was found in men; left- handedness decreased as the
number of repeats increased. For women, left-handers had approximately one more
CAG repeat than right-handers. The researchers believe fewer CAG repeats are
associated with higher levels of testosterone in females. Since left-handedness is
associated with lower levels of testosterone, women with longer CAG repeats were
more likely to be left-handed. For men, fewer CAG repeats are associated with lower
levels of testosterone, which is why men with fewer CAG repeats were more likely to
be left-handed.
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- Limitations/strengths: This research does not answer the question if handedness is
determined by androgen exposure or if it is due to direct effects of the AR gene. A
strength of the study is that it examined both men and women, however, it only
examined twins.
- Relevance: This research is important because it highlights sex differences in terms
of CAG repeats that I will address in my study. According to this study, lower
testosterone levels are found in men with fewer CAG repeats and in women with
longer CAG repeats. Inversely stated, higher levels of testosterone are found in men
with longer CAG repeats, and in women with shorter CAG repeats. This adds to the
inconsistencies in the literature which I hope to help clear up.
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*Nielsen, T. L., Hagen, C., Wraae, K., Bathum, L., Larsen, R., & Brixen, K. (2010).
The impact of the CAG repeat polymorphism of the androgen receptor gene
on muscle and adipose tissues in 20–29-year-old Danish men: Odense
Androgen Study. European Journal of Endocrinology, 162, 795-804. doi:
10.1530/EJE-09-0763
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research was to examine the relationship between the number of CAG
repeats in the androgen receptor and muscle mass, circulating testosterone, and fat.
Researchers hypothesized an inverse relationship between CAG repeats and muscle
mass in young men.
- Method: Participants included 783 Danish men between the ages of 20 and 29 years
old. Participants underwent a physical examination and blood samples were collected
to measure testosterone levels and CAG repeat length. MRI data was collected for
406 participants to measure muscle mass and fat distribution.
- Results: Muscle mass in the thigh and lower trunk areas were inversely related to
CAG repeat length. There was no relationship between CAG repeat length and
circulating testosterone. However, there was a positive relationship between CAG
repeats and estradiol levels.
-Limitations/strengths: The researchers state that a strength of this study is that it
examined younger men, instead of an older male population that would likely
confound results with decreasing levels of testosterone due to aging, obesity,
medications, and chronic disease. This study may be limited by its population of
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healthy, young, Danish men. It does not generalize to women, or those who may not
be as active as the participants.
- Relevance: This study is relevant to my research because it showed no significant
relationship between CAG repeat length and testosterone levels. In addition, though
thigh and lower trunk muscle mass may not be indicators of grip strength, the
relationship between CAG repeat length and grip strength might be an interesting
analysis to run. Based on this study, I would predict an inverse relationship between
grip strength and CAG repeat length.
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*Nummenmaa, L., Hietanen, J. K., Santtila, P., & Hyona, J. (2012). Gender and
visibility of sexual cues influence eye movements while viewing faces and
bodies. Archives of Sexual Behavior, 41, 1439-1451. doi:10.1007/s10508-0129911-0
- Article type/purpose/theoretical orientation/research questions: This primary
research article aimed to examine if eye scanning patterns of models’ faces and
bodies was influenced by clothing or nudity. The authors also investigated the
relationship between the gender of the participant and the gender of the model in
terms of visual scanning. They predicted that the face, chest, and pelvic regions
would receive the most attention, participants would fixate on models of the opposite
sex, and the faces of clothed models would receive the most attention.
- Method study one: Participants included 30 heterosexual males. Their eye
movements were tracked while they viewed 120 pictures of male and female models,
either clothed or nude. After viewing the pictures, participants rated each picture
based on valence (pleasant or unpleasant) and arousal.
Method: study two: Twenty-two heterosexual women and 16 heterosexual men
participated. The methodology of study two is identical to study one.
-Results: For study one, female pictures received the most attention. In the clothed
pictures, faces received the most fixations, whereas the chest and pelvic area received
the most fixations in the nude category. Among all pictures, faces were viewed for the
longest duration. Study two showed a gender difference in fixation, such that women
viewed female and male pictures equally while men fixated on female pictures more
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than male pictures. Men viewed the chest region of models longer than female
participants. Women fixated on male faces more than female faces. In both studies,
participants viewed pictures from top to bottom and faces were the first and longest
fixation.
- Strengths/limitations: Study one was limited because it did not investigate gaze
patterns of females, which is a strength of study two. The materials were limited in
that the posture and facial expressions of the models were not consistent; however,
the variety of pictures increased ecological validity.
-Relevance: This study relates to my thesis because it has a similar methodology.
Based on the findings of this study, I predict that participants in my study will show
gender differences in gaze patterns. Men will most likely fixate on female models
while women will likely fixate on male and female models equally.
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Pasterski, V., Hindmarsh, P., Geffner, M., Brook, C., Brain, C., & Hines, M. (2007).
Increased aggression and activity level in 3- to 11-year-old girls with
congenital adrenal hyperplasia (CAH). Hormones and Behavior, 52, 368-374.
doi:10.1016/j.yhbeh.2007.05.015
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research article was to clear up inconsistencies in the literature regarding the
behaviors of girls and boys with congenital adrenal hyperplasia (CAH). Based on
previous findings, the authors hypothesized that boys would be more active and
aggressive than girls, girls with CAH would be more active and aggressive than girls
without CAH, and boys with CAH would show no differences in activity and
aggression with boys without CAH.
- Methods: Participants were recruited from a larger study about toy preference and
CAH. They were from Los Angeles and London and included 113 children between
the ages of 3 and 11. Thirty eight girls and 29 boys with CAH participated, along with
25 sisters and 21 brothers without CAH. Parents completed the Activity
Level/Extraversion Questionnaire which measured their children’s aggression and
activity level with 17 questions on a 5-point scale.
- Results: Consistent with hypotheses, it was found that boys were rated as more
active and aggressive than girls, girls with CAH were rated as more active and
aggressive than girls without CAH, and there were no differences in activity or
aggression ratings for girls with CAH, boys with CAH, and boys without CAH.
Because the sample consisted of pre-pubertal children, the authors suggest that
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androgens played an organizational role in behavior development, and active and
aggressive behaviors are not necessarily activated by testosterone during puberty.
- Strengths/Limitations: A strength of this study was the sample age. By examining
children, the authors were able to rule out activational effects of pubertal testosterone
as the cause of aggression and activity level in boys and girls with and without CAH.
Additionally, the authors provided suggestions other than organizational effects for
the behavior differences between girls with and without CAH. It may be a possibility
that parents with daughters with CAH may raise them in a more male-typical way and
girls with CAH prefer to play with boys in male-typical games. However, it was
stated that parents of daughters with CAH tend to raise their daughters as highly
feminized. A limitation of this study the broad use of aggression. The authors did not
differentiate between verbal, physical, direct, or indirect aggression. Analyzing
specific aggressive behaviors may have yielded different results.
- Relevance: This study is relevant to my thesis because it shows that there may be
organizational effects of prenatal androgen exposure on masculinized behaviors, such
as aggression, in humans. Though I am not specifically examining participants with
CAH, I do expect to find differences in 2D:4D measurements, which may be an
indicator of prenatal androgen exposure.
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*Penke, L., & Asendorpf, J. B. (2008). Beyond global sociosexual orientations: A
more differentiated look at sociosexuality and its effects on courtship and
romantic relationships. Journal of Personality and Social Psychology, 95,
1113-1135. doi:10.1037/0022-3514.95.5.1113
- Article type/purpose/theoretical orientation/research questions: The aim of this
primary research article was to expand upon the strictly behavior based, global
Sociosexual Orientation Inventory introduced by Simpson and Gangestad (1991).
The authors argue that sociosexual orientation is combined of behaviors, attitudes,
and desires.
- Method, Study One: Study one was an online survey with 1,026 sexually
experienced, heterosexual German men and 1,682 sexually experienced, heterosexual
German women with a mean age of 24.2 years old. All surveys were translated to
German. Participants completed the Self-Perceived Mate Value Scale, the ShortTerm Mating Interest Scale, the Shyness Scale, the Sensation Seeking Scale, the Sex
Drive Questionnaire, a sexuality questionnaire that was a part of the original SOI, and
five items that the authors added to the revised version of the SOI (including current
relationship status, number of lifetime sexual partners, frequency of masturbation,
number of extrapair sexual partners, and number of relationships lasting longer than
one month).
- Results, Study One: For study one, a three-factor model of the original SOI, which
included behavior, attitude, and desire, fit the data well. However, there was only one
item included in the desire subscale. The final SOI-R contained nine total items—
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four from the original SOI and five additional items. Men scored significantly higher
than women on attitude, desire, and total SOI scores. SOI-R scores were significantly
lower for women in relationships as compared to single women, whereas partnered
and single men showed no difference in scores. Partnered men and women had more
restrictive desire scores. Scores on the Short-Term Mating Interest Scale and
Sensation Seeking scale were strongly positively correlated with all subscales of the
SOI-R, whereas shyness was only related to behavior and attitude. Desire scores
were strongly correlated with reported masturbation frequency and scores on the Sex
Drive Questionnaire.
- Strengths/Limitations, Study One: A strength of this study was that the researchers
were successful in creating a three factor model of sociosexuality that better
represented its multifaceted nature than the original global SOI. Additionally, they
demonstrated the importance of separating the SOI into multiple subscales by
showing how different variables (such as shyness) are related to one subscale, but not
the others. However, this study did not demonstrate how sociosexual orientation
affects relationships, which was the aim of the second study.
- Method, Study Two: Participants included 140 partnered, childless, heterosexual
men and 143 women with the same characteristics between the ages of 20 and 30
years old. The study was conducted in a lab with a same-sex research assistant.
Participants completed the SOI and SOI-R, and interacted with an opposite sex
confederate. Interactions were recorded and confederates later rated the participants
on dating interest. Videos interactions were rated for flirtatiousness and body
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language was coded. A follow-up study was conducted online one year later and
included the SOI and SOI-R, as well as questions about participants’ current
relationship status.
- Results, Study Two: Study two presented similar findings in regards to sex
differences in scores on the SOI and SOI-R such that there was a larger sex difference
for the SOI-R and desire showed the largest sex difference. Flirting behavior was
higher amongst those who scored as sociosexually unrestricted on the desire and
behavior subscales. Participants who remained in the same relationship were more
restricted at time one than participants who were single or started a new relationship.
Participants who were in a new relationship at time two were more unrestricted at
time one compared to those who became single and remained single by time two.
Behavior and desire scores were predictive of the number of sexual partners during
the one year period between the study and the follow-up. Single participants and
participants in a new relationship flirted more than those who remained in the same
relationship and those who separated but were single during the follow-up. Couples
in the study had significantly similar scores on the attitude subscale, but no
relationship was found for the behavior and desire subscales.
- Strengths/Limitations, Study Two: A strength of this study was the use of a followup study. Results from time one and time two were compared and demonstrated how
scores on the SOI-R can predict future relationship status and number of sexual
partners. A limitation of this study, and the first study, was the exclusion of
homosexual and bisexual participants.
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- Relevance: This article is relevant to my thesis because it is a thorough examination
of one of my study measures, the SOI-R. It demonstrates that the SOI-R is better than
the original SOI at pinpointing the multiple, and differing, constructs of
sociosexuality. This article provided deep insight into the creation and application of
the SOI-R, which was helpful in the design of my study.
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Perrin, J. S., Herve, P.-Y., Leonard, G., Perron, M., Pike, G. B., … Paus, T. (2008).
Growth of white matter in the adolescent brain: Role of testosterone and
androgen receptor. The Journal of Neuroscience, 28, 9519-9524.
doi:10.1523/JNEUROSCI.1212-08.2008
- Article type/purpose/theoretical orientation/research questions: The aim of this
primary research study was to understand why the growth of white matter in the brain
is so steep in boys, but more gradual in girls. The researchers hypothesized that the
rapid increase in white matter in boys is mediated by testosterone’s effect on
myelination and that CAG repeat length mediates the effectiveness of testosterone.
-Method: Participants included 204 female and 204 male adolescents. Pubertal
development, intelligence, psychopathology, serum levels of testosterone and the
androgen receptor gene were measured. White matter was measured via MRI. The
researchers defined short CAG repeat length as 22 and fewer and long as 23 and
more.
- Results: There was no significant relationship between testosterone levels and CAG
repeat length in males, however the direction of the relationship was negative.
Testosterone mediated the growth of white matter in males with shorter CAG repeat
lengths, but was not a mediator in those with a longer CAG repeat length. It was also
found that males with higher testosterone levels and short CAG repeat lengths were
more likely to show signs of depression.
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- Limitations/strengths: This study is limited because it did not examine (or did not
report) the relationship between white matter growth, testosterone levels, and CAG
repeat length in female participants, even though the data were collected.
- Relevance: This article is relevant to my thesis because it shows that shorter CAG
repeat lengths moderate the effects of testosterone in the direction of stronger
androgenic effects (i.e. greater white matter growth). This is important because a
relationship between testosterone levels and CAG repeat length was not found.
Therefore, it may not necessarily be the case that higher testosterone levels are
responsible for observed differences in individuals; rather it is the sensitivity of the
androgen receptor that may account for differences.
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*Phoenix, C. H., Goy, R. W., Gerall, A. A., & Young, W. C. (1959). Organizing
action of prenatally administered testosterone propionate on the tissues
mediating mating behavior in the female guinea pig. Endocrinology, 65, 369382.
- Article type/purpose/theoretical orientation/research questions: The aim of this
primary research was to determine if hormones played an organizing role on sexual
behavior. Previous studies provided evidence of the activating effects of hormones,
but this study focused on the organizing effects of prenatally administered sex
hormones in guinea pigs.
- Method, Study One: Male and female guinea pigs were studied. Testosterone
propionate was administered to test mothers during gestation, while control mothers
received no hormones. The first study comprised of 14 sexually unmodified female
guinea pigs whose mothers received testosterone, 14 females from control mothers,
nine hermaphrodites (female guinea pigs born with male genitalia), and eight males
from control mothers. All test subjects were gonadectomized between the ages of 90
and 160 days old, then administered estradiol benzoate followed by progesterone.
Tests were conducted hourly to test for male sexual behavior, such as mounting.
- Results, Study One: The test females and castrated males showed no signs of
lordosis. Duration of heat increased in the control groups as the amount of
administered estradiol increased. Hermaphrodites and castrated males demonstrated
mounting behavior before and after the administration of hormones, whereas the
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control and unmodified females only demonstrated mounting behaviors after the
administration of hormones.
- Method, Study Two: Study two contained four groups of previously studied
subjects, including three hermaphrodites, seven sexually unmodified females, eight
control females, six hermaphrodites and six normal females who were injected, daily,
with testosterone propionate, five mothers of hermaphrodites who were treated with
testosterone during pregnancy, and eight control females. The mothers and control
females were gonadectomized between the ages of one and three years. All subjects
were administered estradiol benzoate and progesterone following the same protocol
of study one.
- Results, Study Two: The unmodified females showed a significant increase in
mounting behaviors, as did the hermaphrodites. However, the behavior of the
hermaphrodites was not statistically evaluated. The normal females showed mixed
mounting responses. Normal females who received testosterone after birth were able
to display lordosis after treatment stopped. However, hermaphrodites never regained
the ability to display lordosis. The mothers who received testosterone propionate
during pregnancy continued to display lordosis.
- Method, Study Three: Subjects consisted of five hermaphrodites, five normal
females, and eight castrated males. All subjects received testosterone propionate for
16 consecutive days when they reached the age of 180 days old. Each animal
completed a sexual behavior test before injections and eight more sexual behavior
tests during and after the injection period.
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- Results, Study Three: Hermaphrodites and normal females demonstrated no
mounting behaviors prior to injections, whereas males demonstrated approximately
5.5 mounting behaviors. After injections, there were no significant differences in
sexual behavior between the hermaphrodites and males, and these two groups differed
significantly from the normal females.
- Method, Study Four: Subjects consisted of five males from mothers who did not
receive testosterone during pregnancy, five males whose mothers did receive
testosterone during pregnancy, and five males who received postnatal testosterone in
addition to having mothers who received testosterone during pregnancy. Each male
was presented with a female and their sexual behaviors were recorded.
- Results, Study Four: Males who received prenatal testosterone demonstrated more
masculine mating behaviors than those who did not receive prenatal testosterone, but
this finding was not significant.
- Strengths/Limitations: A strength of these studies is that they demonstrate
organizational effects of androgens on sexual behavior related not only to genital
tissues, but also to neural tissues. This article was the first to draw these conclusions.
An additional strength was the examination of male and female groups who received
testosterone at different periods of development, or didn’t receive it at all. By doing
this, the researchers were able to conclude that testosterone has the strongest effects
on mating behavior when administered prenatally. A limitation of this research is that
digit ratio was not examined.
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- Relevance: This article is relevant to my thesis because it was the first to
demonstrate that androgens administered prenatally permanently alter mating
behaviors, whereas postnatal androgens do not. This is important because it shows
the organizing effects of androgens. This relates to 2D:4D research because 2D:4D is
a measure of prenatal androgen exposure, and may be indicative of the organizing
actions of androgens on later sexual behavior.
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*Putz, D. A., Gaulin, J. C., Sporter, R. J., & McBurney, D. H. (2004). Sex hormones
and finger length: What does 2D:4D indicate? Evolution and Human
Behavior, 25, 182-199. doi:10.1016/j.evolhumbehav.2004.03.005
- Article type/purpose/theoretical orientation/research questions: This primary
research consists of two studies and is based on the finding that high levels of
prenatal androgens tend to yield a low, or masculine, 2D:4D ratio. A relationship
between 2D:4D and sexual orientation, status, voice pitch, sociosexuality and mating
success were predicted.
- Method first study: 111 heterosexual males participated in the first study. After
being told they would be competing with another man to go on a date with a woman,
their voice was recorded as they read a passage aloud, described themselves to the
woman, and explained why other men should admire them. Following a simulated
dating game, participants completed self-assessments of their social and physical
dominance, interest in the woman, and previous mating success, in addition to
completing the sociosexual orientation inventory. Four 2D:4D measurements were
obtained from photocopies and included right and left hand, average, and the
difference between right and left.
- Method second study: The second study consisted of 119 male and 120 female
participants. Right and left hand 2D:4D was measured. Participants completed a
mental rotation test, the SOI, sexual history survey, and provided their sexual
orientation. Similar data from both studies were combined for analysis.
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- Results: 2D:4D differed significantly between men and women; however, the
difference between right and left 2D:4D was not different, and thus not a reliable
measure of androgen exposure. All variables showed sex differences: males scored
higher on mental rotation task, females had lower SOI scores, and females had higher
number of sexual partners and potential conceptions. The only variable significantly
related to 2D:4D (and only for the left hand) was sexual orientation for both males
and females.
- Limitations/strengths: The authors state that 2D:4D is itself a limitation, given that it
only predicted 5 out of 57 sexually dimorphic traits. 2D:4D may not be a valid
predictor of these traits that depend on sex hormones, even though it predicts these
hormone levels. It is suggested that 2D:4D is only indicative of sex hormone levels at
the time of sexual differentiation.
- Relevance: This article is relevant to my thesis because I will be measuring 2D:4D.
Left hand 2D:4D is the measurement that yielded the most predictive results for this
study. However, there are conflicting results that suggest other measurements of
2D:4D may be more reliable. I will use this information as a guideline to take
multiple measurements of 2D:4D.
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Rammsayer, T. H., & Troche, S. J. (2007). Sexual dimorphism in second-to-fourth
digit ratio and its relation to gender-role orientation in males and females.
Personality and Individual Differences, 42, 911-920.
doi:10.1016/j.paid.2006.09.002
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research article was to replicate and expand upon the findings of Csathó et al.
(2003) which stated that females with a lower 2D:4D ratio scored as more masculine
than females with a higher 2D:4D ratio when measured with the Bem Sex-Role
Inventory (BSRI). The current authors expanded this research by including both
males and females and by analyzing the various scales of the BSRI independently.
- Methods: Participants included 312 women and 423 men between the ages of 18 and
36 years old who were all German, right-handed, and heterosexual. Ethnicity,
handedness, and sexual orientation were all controlled due to possible differences in
2D:4D among different groups. 2D:4D was measured twice for each hand by a
research assistant using a Vernier caliper. Final measurements for each hand were
obtained by averaging the two measurements. Participants completed the BSRI which
included 20 masculine adjectives, 20 feminine adjectives, and 20 gender-neutral
adjectives. Each adjective was rated on a 7-point scale to determine how well it
described the participant. Androgyny scores were calculated from the t ratio of the
difference between the masculine and feminine subscale scores.
- Results: Men’s right hand 2D:4D was significantly lower than women’s, but no sex
difference was found for left hand 2D:4D. Women scored higher than men on the
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femininity subscale and men scored higher than women on the masculinity subscale.
No significant relationships were found for women’s BSRI scores and 2D:4D
measurements. A positive relationship between men’s left-hand 2D:4D and scores on
the BSRI femininity subscales was found. The results of the current study did not
replicate those of Csathó et al. (2003).
- Strengths/Limitations: A strength of this study was that it improved upon Csathó et
al.’s previous similar study by greatly increasing the sample size. However, the lack
of diversity of the sample may have limited their findings. Though the authors were
unable to replicate the previous results, they provided possible alternate explanations,
such as environmental influence, that may account for lack of relationship between
2D:4D ratios and sex-role identification. However, it may be that their measure of
sex-roles is to blame. The BSRI was created in the 1970s and may not currently
represent today’s ideas of stereotypical sex-roles. Additionally, there may be cultural
differences in terms of what is defined as masculine and feminine.
- Relevance: This study is relevant because it examines similar variables that I will
investigate in my thesis. Though I am not directly measuring sex-roles, I am
measuring sociosexual orientation and competition. High scores for these variables
may indicate masculinity, which I would predict to be related to lower 2D:4D ratios.
Though the researchers did not find significant relationships between 2D:4D and
masculinity, I believe it was due to an outdated measure and lack of sample diversity,
given that results were inconsistent with similar studies.
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*Rosvall, K. A. (2011). Intrasexual competition in females: Evidence for sexual
selection? Behavioral Ecology, 22, 1131-1140. doi: 10.1093/beheco/arr106
- Article type/purpose/theoretical orientation/research questions: This review is based
on the theory of sexual selection which includes traits involved in competing for
mates. The author predicts that females, like males, compete for mates. Her
hypotheses are when the sex ratio is low females will compete for mates, females
compete for the males who provide direct and indirect (genetic) benefits, and
intrasexual competition among females should increase when resources are low.
- Method: In order to determine if her predictions are true, the author reviews several
past research articles.
- Results: Based on past observational and experimental research, sand gobies, mice,
and human females do compete for mates when the operational sex ratio is low. In
species in which males care for offspring, there is high female-female competition.
There is less competition for mates in species which do not care for offspring.
Females compete for mates with preferred genetic qualities, such as attractiveness.
Subordinate females in species that live in groups experience delayed reproduction
from stress caused by the aggressive female members of the group. Females compete
for quality of mates, not quantity.
- Strengths/Limitations: This review focuses primarily on intrasexual competition
amongst female animals, particularly birds, rodents, and insects. There is likely very
little past research that focuses on sexual selection and mating competition amongst
women. However, a strength is that the author did point out that women compete for
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mates when the sex ratio is low. The author stated that past research shows higher
competition amongst females of species that provide care for offspring (especially in
species with paternal care). She does not report if this is the case for humans, though
it may be, since men provide parental care.
- Relevance: The most relevant portion of this review is the finding that there is
intrasexual competition amongst women when the sex ratio is low. Given that the sex
ratio is currently low, I predict that the women in my study will be competitive (spend
more time looking at women they consider their competition, and rate the female
models as high in competition).
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*Rowe, D., Vazsonyi, A., Figueredo, A. (1997). Mating-effort in adolescence: A
conditional or alternative strategy. Pergamon, 23, 105-115. doi:
10.1016/S0191-8869(97)00005-6
- Article type/purpose/theoretical orientation/research questions: The theoretical
orientation of this primary research was the idea that the lack of a conscience may be
beneficial in a mating context; specifically, it may increase mating effort. They
hypothesized that mating effort and delinquency would not be correlated when social
failure was controlled for, those with a low mate value would have increased mating
effort and delinquency, those who are sexually successful would also show increased
mating effort, and mating effort would not show heritability.
- Method: Participants included 60 male twin pairs and 56 female twin pairs with a
mean age of 16.8 years old. The study consisted of an at-home interview and the
participants completed the Mating Effort Scale (designed for the purpose of this
study), and measures of mate value, delinquency, social failure, and sexual activity.
- Results: Mating effort and delinquency were significantly correlated when social
failure was controlled for. Low mate value was not significantly correlated with
mating effort; however, mating effort was higher for attractive boys and for girls who
were not interested in parental investment. Mating effort and number of sexual
partners was positively correlated for boys, which did not support the hypothesis.
Contrary to the fourth hypothesis, delinquency and mating effort were correlated
between siblings.
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- Strengths/Limitations: A strength of this study was the attempt to determine whether
social failure leads to high mating effort or if mating effort is explained by genetics.
While ambitious, I feel that no solid conclusions can be made based on the young age
of the participants and the lack of controlling for environmental factors. The
participants, being young with stable living environments, had not experienced any
significant social failure in their lives. Therefore, this variable cannot be confidently
researched in children.
- Relevance: This article is relevant to my thesis because I examined the Mating
Effort Scale in my exploratory analyses. Based on the extremely low reliability for
this scale in my sample, I feel that the Mating Effort Scale is not an appropriate
measure for adults. Additionally, it may not be a reliable measure of mating effort, as
the questions do not directly measure it.
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*Rupp, H., & Wallen, K. (2007). Sex differences in viewing sexual stimuli: An eyetracking study in men and women. Hormones and Behavior, 51, 524-533.
doi:10.1016/j.yhbeh.2007.01.008
- Article type/purpose/theoretical orientation/research questions: This primary
research examined differences between men and women (either normal cycling, or
using oral contraceptives) in how they view explicitly sexual images. It was predicted
that males would fixate more on explicit portions of the pictures, while females
(especially those using oral contraceptives) would fixate more on faces, background,
and clothing.
- Method: Participants included 15 men, 15 normal cycling women, and 15 oralcontraceptive using women. They completed a brief demographic questionnaire,
questions from the Brief Index of Sexual Function, and the Sexual Permissiveness
subscale of the Sexual Attitudes Scale.
Participants were screened for heterosexual preference and some experience
with pornography.
Three testing sessions were completed for all participants so the normal
cycling women could be tested during each phase of their menstrual cycle.
Participants viewed 72 randomized pictures of heterosexual couples engaging in
intercourse or oral sex per each testing session. Participants filled out a trait anxiety
questionnaire, were then calibrated to the eye-tracker, and began viewing the stimuli
one by one at their own pace, with a 1-sec fixation slide between each picture. After
viewing all pictures, participants viewed them again in a new random order and rated
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each picture on a nine-point scale of sexual attractiveness. Fixations were calculated
on seven look zones: female face, male face, genitals, female body, male body,
clothing, and background. Measures of attention were first fixation, percent time, and
looking probability.
- Results: Forty two of the 45 participants completed all three sessions. Participants
who were more recently sexually active rated the pictures as more sexually attractive.
Men and both groups of women rated the stimuli equally in sexual attractiveness.
Men spent more time viewing and had a higher probability of looking at female faces
than both groups of women. Men were least likely of the groups to look at male faces.
Normal cycling women looked at genitals more than contraceptive-using women and
men. Contraceptive-using women looked more at the clothing zone than the other
groups, and men were more likely to first look at the background than both groups of
women. Oral contraceptive-using women spent more time looking at the background
than the other groups. By the third session, all participants spent less time looking at
the genital zone and more time looking at the female body zone.
-Strengths/limitations: The sample size was quite small and results may not
generalize to the public. The authors state a limitation to using an eye-tracker is that
eye-tracking displays where a participant looks, but not why they are looking there.
Additionally, it may be difficult to gage attention to sexual stimuli because of social
stigma and discomfort. However, a strength of this study was the inclusion of female
participants, as well as the differentiation between normal cycling and contraceptiveusing female groups. Since the normal cycling women looked at genitals more than
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the oral contraceptive-using women, a strength of this study is that it shows that there
is likely a hormonal influence on attention.
- Relevance: This study utilized an eye-tracker, used pictures of men and women in a
very literal mating situation, and examined sex differences. Though my thesis does
not include pictures of couples mating, my stimuli may be more ecological
representations of social mating behaviors.
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*Sacco, D. F., Hugenberg, K., & Sefcek, J. A. (2009). Sociosexuality and face
perception: Unrestricted sexual orientation facilitates sensitivity to female
facial cues. Personality and Individual Differences, 47, 777-782.
doi:10.1016/j.paid.2009.06.021
- Article type/purpose/theoretical orientation/research questions: This primary
research article consists of two studies that examine the role of sociosexual
orientation in perceiving facial symmetry (study one) and smile sincerity in pictures
of male and female faces (study two). The researchers predicted that those who are
sociosexually unrestricted would better identify facial symmetry (a marker of genetic
quality) than those who are sociosexually restricted. Additionally, they predicted that
those who are sociosexually unrestricted would accurately distinguish between
deceptive and genuine smiles.
- Method study one: Participants consisted of 39 women and 24 men, (60 Caucasian,
2 Hispanic, and 1 other). They viewed 18 pictures of male and female faces (3 low
symmetry, 3 normal symmetry, and 3 high symmetry) and rated each picture on a 7
point scale of attractiveness. Participants then completed the original unrevised
Sociosexual Orientation Inventory and a demographics questionnaire.
- Method study two: One-hundred seventeen females and 61 males (167 Caucasian, 5
African-American, and 6 other) completed study two. Participants viewed 20 movie
clips of a person displaying a neutral facial expression, then smiling (10 were
genuine, 10 were deceptive), and returning to the neutral facial expression. Following
each video, participants noted whether the smile was genuine or deceptive. They then
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completed the original unrevised Sociosexual Orientation Inventory and a
demographics questionnaire.
- Results: In study one, there was no significant correlation between restricted
orientation and attractiveness ratings, though restricted individuals were more likely
to rate symmetrical faces as attractive. As predicted, there was a significant
interaction between unrestricted individuals and attractiveness ratings for symmetrical
faces, but only for female faces. All participants perceived asymmetrical faces as
unattractive. In study two, regardless of sociosexual orientation, participants were not
able to determine the sincerity of male smiles. However, participants with an
unrestricted orientation were significantly better than those with a restricted
orientation to distinguish between genuine and deceptive female smiles.
- Strengths/Limitations: A limitation of this study is that the actors in the videos and
models in the photographs were not in an ecological setting. However, a strength of
the second study is the use of video instead of static photographs. I believe that facial
expressions may be better perceived in motion. An additional limitation of these
studies is the use of the original SOI instead of the SOI-R. The revised inventory may
yield more significant results as there are multiple facets to sociosexual orientation.
- Relevance: This article is relevant to my study because it shows that men and
women who are sociosexually unrestricted are better at perceiving symmetrical faces
as attractive and distinguishing between genuine and deceptive smiles for females.
Based on this, I predict that in my study, those who are unrestricted will pay more
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attention to female models. This is consistent with female intrasexual competition and
previous eye-tracking studies that suggest both men and women look at females.
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*Schwarz, S., Mustafić, M., Hassebrauck, M., & Jörg, J. (2011). Short- and LongTerm Relationship Orientation and 2D:4D finger-length ratio. Archives of
Sexual Behavior, 40, 565-574. doi:10.1007/s10508-010-9698-9
- Article type/purpose/theoretical orientation/research questions: This article consists
of two primary research studies that examine the role 2D:4D plays in Short- and
Long-Term Relationship Orientation. The authors predicted that those with a lower
2D:4D ratio would be more likely to exhibit a Short-Term Relationship Orientation. It
was predicted that 2D:4D would not be related to Long-Term Relationship
Orientation because that is more likely to be influenced by oxytocin levels and
attachment style.
- Method study one: The first study only examined males. Participants included 91
German men whose mean age was 24.3 years old. Measures consisted of the
Relationship Orientation Questionnaire which included two scales (Short-Term
Relationship Orientation and Long-Term Relationship Orientation), and 2D:4D
measurements via digital scan.
- Method study one: One-hundred forty-two German women and 65 German men
whose mean age was 23.89 years old participated in the second study. Participants
completed the Relationship Orientation Questionnaire, the unrevised Sociosexual
Orientation Inventory, a scale of social desirability, and a measure of sex drive.
2D:4D ratios were measured via digital scan.
- Results: Women scored higher on Long-Term Relationship Orientation and social
desirability than men. Men scored significantly higher than women on Short-Term
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Relationship Orientation, sociosexual orientation, and sex drive. In study one, men’s
right hand, but not left hand, 2D:4D was related to Short-Term Relationship
Orientation. In study two, men’s left hand 2D:4D measurements correlated with
Short-Term Relationship Orientation, but women’s 2D:4D measurements did not. As
predicted, there was no correlation between Long-Term Relationship Orientation and
2D:4D measurements. Men scored higher on Short-Term Relationship Orientation
than women. No significant correlations were found between SOI scores and 2D:4D
measurements.
- Strengths/Limitations: A limitation of this study is that the researchers did not take
sexual orientation into account. Though there are mixed findings, it has been found
that heterosexual women have higher 2D:4D ratios than lesbians. Additionally, the
researchers used the original global SOI instead of the SOI-R which measures
attitudes, desires, and behaviors. They may have found correlations between 2D:4D
measurements and the SOI scales. A strength of the second study is that participants
consisted of both men and women. An additional strength is that the authors provided
the full Relationship Orientation Questionnaire in the article. The Short-Term
Relationship scale is very similar to questions on the SOI-R; however, the Long-Term
Relationship scale does not seem to be related to the SOI-R.
- Relevance: This study is relevant to my thesis because it examined two variables I
will also examine: 2D:4D measurements and sociosexual orientation. The researchers
found no correlations between 2D:4D and scores on the original SOI, due to, what I
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believe is, a flaw in their measures (not using the revised SOI). I still predict that
scores on the SOI-R will be negatively correlated with 2D:4D measurements.
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*Sell, A., Cosmides, L., Tooby, J., Sznycer, D., von Rueden, C., & Gurven, M.
(2010) Human adaptations for the visual assessment of strength and fighting
ability from the body and face. Proceedings of the Royal Society, 276, 575584. doi:10.1098/rspb.2008.1177
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research article was to determine if humans are capable of assessing upper
body strength, and thus formidability, based on male faces. The theoretical
orientation is that human ancestors evolved to quickly determine the fighting ability
of other male humans when very little information was provided. The researchers
hypothesized that participants would be able to correctly assess the strength and
fighting ability of men based only on photographs, upper body strength would be
correlated with strength perception and fighting ability, men would be better at
predicting strength than women, and participants would be able to assess the strength
of members of other cultures.
- Method: For the first study, 59 American men posed for facial and body
photographs and their strength was assessed using various weight-lifting machines.
These photographs (whole man, body only, and face only) were judged by 142
college students based on their perceived physical strength as compared to other men
of the same age. Thirty-seven different participants rated the full-body photographs
based on fighting formidability. The second study stimuli consisted of 109 American
men and 146 American women who also posed for body and facial photographs and
their strength was measured. Following the same procedure as study one, 132
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participants rated the photographs. For the third study, similar photographs were
taken of 53 Tsimane men and their strength was measured. Thirty-two American
college students rated the pictures of the Tsimane men’s faces based on perceived
strength. For the fourth study, 28 Andean men were photographed, their strength was
assessed, and their faces were rated based on strength by 28 American
undergraduates.
- Results: For all cultures photographed, participants could accurately assess the
strength of the models based on facial images alone, and perceived fighting ability
was positively correlated with perceived strength. Participants were able to
successfully assess the strength of women based on body photographs and, to a lesser
degree, facial photographs.
- Strengths/Limitations: A strength of these studies was the examination of multiple
cultures as stimuli for strength assessments. However, a limitation was that only
American college students assessed the photographs. The study would have benefited
to use participants from multiple cultures to rate the strength of the photographs.
- Relevance: This article is relevant to my thesis because it demonstrates that facial
photographs can cue actual physical strength. This is important because participants
in my study may fixate on the men that they deem the strongest, and thus the highest
competition for men and the ideal partner for women.
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*Simpson, J. A., & Gangestad, S. W. (1991). Individual differences in sociosexuality:
Evidence for convergent and discriminant validity. Journal of Personality and
Social Psychology, 60, 870-883. doi:10.1037/0022-3514.60.6.870
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research article was to determine if there was an underlying factor for
sociosexual behaviors and attitudes, assess the validity of the SOI (created for the
purpose of this study), and determine if sociosexuality was related to sex drive and
frequency of sex.
- Method, Study One: This article contains six studies. The first consisted of 204
male and 202 female college students who completed the original version of the SOI.
The original SOI contained 11 items that measured overt and covert sexual behavior
and attitudes regarding uncommitted sex.
- Results, Study One: For the first study, the authors found that the items of the SOI
that loaded the most highly were those that directly measured participants’
willingness to engage in uncommitted sex. However, frequency of sex did not load
highly. The five items that loaded highly became the SOI.
- Method, Studies Two, Three, Four, Five, and Six: For the second study, 144
heterosexual couples completed the five-item version of the SOI and reported how
long they dated before engaging in sex. Study three consisted of 309 men and 296
women who completed the SOI and reported if they had engaged in sex with their
current partner and if they had ever cheated on this partner. The fourth study used the
same 144 couples from the second study, who again completed the SOI, as well as
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commitment, investment, love, and dependency scales. For the fifth study,
participants included 241 heterosexual couples completed the SOI and reported the
number of times they had sex in the past month. For the sixth study, participants
included 197 men and 199 women who completed the SOI and Eysenck’s Inventory
of Attitudes to Sex.
- Results, Studies Two, Three, Four, and Five: For study two, couples who scored as
unrestricted on the SOI engaged in sex sooner than those who scored as restricted.
For study three, those who scored as unrestricted were more likely to have engaged in
sex outside of their current relationship than those who scored as restrictive. Results
of study four indicated that restricted individuals expressed greater commitment,
investment, love, and dependency as compared to unrestricted individuals. For study
five, frequency of sex did not correlate with scores on the SOI. For study six, the SOI
was not correlated with satisfaction, sexual shyness, or neurotic sex. SOI was
positively moderately correlated with impersonal sex, permissiveness, pornography,
aggressive sex, and physical sex, and negatively correlated with prudishness.
- Strengths/Limitations: A strength of these studies was that the authors went to great
lengths to assess the convergent validity of a measure they created, the SOI, by
conducting six separate studies. This research also provides further insight into
relationship formation and maintenance such that sociosexually restricted and
unrestricted individuals likely prefer different types of mates and relationships that
require different methods of maintenance. For example, those who are restricted
require more love, commitment, dependency, and investment from their partner than
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those who are unrestricted. A limitation of the original SOI was that, though it
measured three constructs—overt sexual behavior, covert sexual behavior, and
attitudes—it was not equally divided into the subscales. For example, only one item
measured attitudes towards uncommitted sex.
- Relevance: This article is relevant to my thesis because it demonstrates the
usefulness of the original SOI. Although I used the SOI-R, this article demonstrates
that the original SOI was in fact a valid measure of sociosexual orientation. The fact
that I used a further revised version only strengthens the validity of my research.
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*Stenstrom, E., Saad, G., Nepomuceno, M. V., & Mendenhall, Z. (2011).
Testosterone and domain-specific risk: Digit ratios (2D:4D and rel2) as
predictors of recreational, financial, and social risk-taking behaviors.
Personality and Individual Differences, 51, 412-416.
doi:10.1016/j.paid.2010.07.003
- Article type/purpose/theoretical orientation/research questions: The purpose of this
primary research was to determine if 2D:4D was related not only to financial risktaking—which has been shown in previous studies—but also to recreational, health,
social, and ethical risk taking. The researchers hypothesized that lower, more
masculine 2D:4D would be related to higher risk taking behaviors in all of the
domains for both men and women.
- Method: Participants included 219 male and 194 female Canadian college students
with a mean age of 20.9 years old. They completed a demographics questionnaire
and a risk taking survey that contained ten items each for the five aforementioned risk
taking categories. Finger measurements were conducted by trained researchers using
digital calipers and included right hand 2D:4D and right hand rel2, which compares
the length of the second digit to the sum of the lengths of the other four digits. Each
of the three experimenters measured the digits of 22 additional students twice each to
establish repeatability before the study began.
- Results: Independent groups t-tests revealed that men engaged in more risky
behaviors than women for all five of the risk taking categories and men had lower
2D:4D and rel2 than women. When the largest ethnic group, Caucasian, was
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analyzed separately, men’s digit ratios negatively correlated with recreational,
financial, social, and overall risk taking. When the entire male sample was analyzed,
only financial and overall risk taking were negatively correlated with 2D:4D, while
only overall risk taking was negatively correlated with rel2. Neither digit ratio was
correlated for any of the risk taking categories for women. There were no significant
differences in predictive ability between 2D:4D and rel2.
- Strengths/Limitations: A strength of this study was the examination of multiple
types of risk taking. While previous research has only shown a relationship between
digit ratio and financial risk taking, this study demonstrated that financial, social,
recreational, and overall risk taking is negatively associated with digit ratio in men.
Additionally, this study emphasized the importance of examining ethnic groups
separately, as previous research has shown differences in 2D:4D measurements
among different ethnicities. A limitation of this study was that only the digit ratio of
the right hand was measured. Since there have been previous significant findings
regarding left hand 2D:4D, the researchers should have measured both hands.
- Relevance: This study is relevant to my thesis because it demonstrates that digit
ratio is related to behaviors in men, but not in women. This shows me that it is more
likely that men will have stronger between 2D:4D and my study variables as
compared to women. Also, this study further supports the notion that prenatal
testosterone has later effects on behavior, specifically, risk taking.
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*Thornton, J., Zehr, J. L., & Loose, M. D. (2009). Effects of prenatal androgens on
rhesus monkeys: A model system to explore the organizational hypothesis in
primates. Hormones and Behavior, 55, 633-645.
doi:10.1016/j.yhbeh.2009.03.015
- Article type/purpose/theoretical orientation/research questions: This article reviewed
various studies that examined the role of prenatal testosterone in the physical,
behavioral, and sexual development of rhesus monkeys. The authors aimed to test
whether the Organizational Hypothesis proposed in 1959 applies to nonhuman
primates. This hypothesis posits that prenatal androgens can permanently alter the
neural circuitry leading to changes in sexually dimorphic behaviors.
- Methods: The authors reviewed various research articles and books written since
1959 that pertained to the role of prenatal androgens in the sexual and behavioral
development of rhesus monkeys.
- Results: Review of previous research showed that there is an organizational effect of
prenatal androgens in rhesus monkeys. It was found that administration of prenatal
testosterone and/or dihydrotestosterone yielded masculinized and defeminized
external genitalia, masculinized juvenile behaviors including mounting, rough play,
and vocalizations, and masculinized adult mounting behavior and defeminized
proceptive behaviors. Behaviors that were not altered by prenatal androgen exposure
were juvenile infant interest and adult presenting behaviors. The authors concluded
that the prenatal period is especially sensitive to androgen exposure and the effects of
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this exposure are permanent. Additionally, they conclude that prenatal androgens
organize the neural circuitry responsible for mating behaviors.
- Strengths/Limitations: A strength of this article is that it reviewed all relevant prior
research in this area and did not focus solely on the articles that supported the
Organizational Hypothesis. A limitation of this research is that it may not directly
apply to humans. Though rhesus monkeys are much more closely related to humans
than guinea pigs (the original subjects of the first study of the Organizational
Hypothesis), they serve as only a proposed model of the effects of prenatal androgen
exposure in humans.
- Relevance: This review is relevant to my thesis because it explores the
Organizational Hypothesis in great depth in a population that may share similarities
with humans. Since I am investigating a marker of prenatal androgen exposure,
2D:4D, it is important to understand the underlying theory that my research is based
on.
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Turakulov, R., Jorm, A. F., Jacomb, P. A., Tan, X., & Easteal, S. (2004). Association
of dopamine-b-hydroxylase and androgen receptor gene polymorphisms with
Eysenck’s P and other personality traits. Personality and Individual
Differences, 37, 191-202. doi:10.1016/j.paid.2003.08.011
- Article type/purpose/theoretical orientation/research questions: This primary
research article examined the role of CAG and GGC repeats, as well as dopamine-bhydroxylase, in psychoticism.
- Method: Participants were contacted via phone call and later interviewed in person,
and included White Australian adults, 896 of whom were genotyped for DBH, 1676
of whom were genotyped for CAG repeat length, and 1698 of whom were genotyped
for GGC repeat length. Participants completed the BIS/BAS scales and the Eysenck
Personality Questionnaire-Revised.
- Results: Males who scored high in psychoticism were more likely to have short
CAG repeats. The same trend was found for women, but it did not reach significance.
Though it was not significant, there was a trend showing higher scores for
psychoticism in participants with shorter CAG repeat lengths. Women with short
CAG repeats and men with short GGC repeats scored high on a scale measuring
drive.
- Limitations/strengths: A limitation of the finding regarding drive and repeat length
is that the researchers conducted 28 statistical tests and may have committed a Type I
error. A strength of the study was the very large sample size, although the authors
report that the correlations were relatively weak for such a large sample size.
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- Relevance: This study provides support that CAG repeat length may be related to
personality traits. Though psychoticism is not being addressed in my thesis, these
findings do show that there may be a genetic predisposition to certain personality
traits. Psychoticism would be most closely related to competitiveness in my study, so
this may provide further support that those with shorter CAG repeat lengths will
spend more time looking at models they regard as their competition.
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Von Eckardstein, S., Syska, A., Gromoll, J., Kamischke, A., Simoni, M., &
Nieschlag, E. (2001). Inverse correlation between sperm concentration and
number of androgen receptor CAG repeats in normal men. The Journal of
Clinical Endocrinology and Metabolism, 86, 2585-2590.
- Article type/purpose/theoretical orientation/research questions: This primary
research study aimed to examine the effects of CAG repeat length on spermatogenesis
based on their hypothesis that the androgen receptor plays a role in sperm count.
- Method: Participants were drawn from previous male contraceptive and infertility
studies and consisted of 131 control males (normal spermatogenesis) and 43 infertile
males. Serum levels of testosterone, LH and FSH were collected, as well as DNA
data from blood samples, and a sample of ejaculate.
- Results: No relationship between CAG repeat length and testosterone levels were
found. An inverse relationship was found between CAG repeat length and sperm
count, meaning that men in the fertile population with short CAG repeat lengths had
the highest sperm output. There was no correlation between CAG repeat length and
sperm output in the infertile group. The authors suggest that a high number of CAG
repeats is related to decreased androgen receptor activity.
- Limitations/strengths: The authors admit that the absence of a relationship between
testosterone and CAG repeat length was unexpected, and reasoning for this absence
was not provided. However, a strength of the study is that it differentiated between
the role CAG repeat length plays in spermatogenesis in normal males versus infertile
males, such that CAG repeat length does not affect or cause male infertility.
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- Relevance: In addition to Nielsen et al., this study found no relationship between
CAG repeat length and testosterone. This is relevant because it highlights the
importance the polymorphism plays in androgen sensitivity, regardless of testosterone
levels.
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*Weege, B., Lange, B. P., & Fink, B. (2012). Women’s visual attention to variation in
men’s dance quality. Personality and Individual Differences, 53, 236-240.
doi:10.1016/j.paid.2012.03.011
- Article type/purpose/theoretical orientation/research questions: The theoretical
orientation of this primary research was that women able to perceive the health,
physicality, and attractiveness of men based on their dancing skills. The researchers
hypothesized that women would fixate longer on male avatars that they perceived to
be “good” dancers, and thus more attractive and masculine, as compared to those
perceived as “bad” dancers.
- Method: Participants included 50 women with a mean age of 23.9 years old who
viewed five ten second video clips of “good” male dancing avatars, and five ten
second video clips of “bad” male dancing avatars while connected to an eye tracker.
Video clips were rated on dance quality during a previous study. A bad and good
dancer was presented on the screen simultaneously, 25 times, and fixation times were
measured. Participants then viewed each video again, individually, and rated them
based on attractiveness. The sample was later reduced to 46 participants due to
calibration errors for the eye tracker machine.
- Results: Consistent with the hypothesis, women tended to fixate on the good dancers
for a longer amount of time than the bad dancers, and rated the good dancers as
attractive and masculine. Number and length of fixations significantly positively
correlated with attractiveness ratings. A similar, but non-significant relationship was
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found for masculinity ratings. Attractiveness and masculinity ratings were positively
correlated.
- Strengths/Limitations: The use of featureless male avatars was both a strength and
limitation. By omitting facial features, muscle tone, clothing style, and ethnicity, the
researchers were able to solely measure fixation on dance quality, and thus
attractiveness and masculinity. However, thus use of featureless avatars demonstrates
very low ecological validity and findings may not be generalizable to real world
situations.
- Relevance: This study is relevant to my thesis because it demonstrates that women
tend to fixate more often and for a longer amount of time on males that they deem to
be attractive. Though the stimuli in this study differ from the stimuli in my study,
similar results may translate to still pictures of real men in a bar/club atmosphere.