Download Chapter 8-Evolutionary Theory

Evolutionary Perspectives on Personality
Part Two. Biological Domain

Chapter 6: Do our genes influence our
personality traits?

Chapter 7:Do our physiological systems
(e.g., brain, peripheral nervous system)
influence our personality traits?

Chapter 8: How are personality traits
adaptive (Evolutionary Theory)?
© 2015 M. Guthrie Yarwood
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Lecture Outline

3 Ways personality became an adaptation
 Natural Selection, 2 Types of Sexual Selection

2 Evolutionary Explanations for Individual
Differences
 Fluctuating Optimum, Frequency Dependence

Sex Differences in Personality

Altruism and Inclusive Fitness
© 2015 M. Guthrie Yarwood
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Adaptation requirements
A gene mutation developed to solve an adaptive problem.






Inherited characteristics
develop in most or all species members
produced by natural selection
because they solved an adaptive problem—
functionality
must have contributed to reproductive success, directly
or indirectly
need not be present at birth (teeth, breasts, beards,
desires, emotions, personality traits, etc.)
Adapted from
homepage.psy.utexas.edu
© 2015 M. Guthrie
Yarwood
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3 Ways Personality Traits Became
Adaptations

Natural Selection

Sexual Selection
 Intrasexual Competition
 Intersexual Competition
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Natural Selection

Determines whether a mutation should
be removed from the population or
spread throughout the population.

Mutation – a change in gene structure
when the gene is being passed on to
future generations.
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Natural Selection
Problematic
Mutations
Beneficial
Mutations
↓ Production
/ Death
↑ Production /
Survival
© 2015 M. Guthrie Yarwood
Slowly
Spreads
through
population
Removed
from
population
Adaptation
7
Personality Traits as Adaptations:
What adaptive problems do the Big Five solve?
O
• High vs. Low
C
• High vs. Low
E
• High vs. Low
A
• High vs. Low
N
• High vs. Low
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Personality Traits as Adaptations:
What adaptive problems do the Big Five solve?
Finding a valuable mate
 Dangerous vs. Safe Environments
 Finding food, shelter
 Protection
 Advancements in technology
 Leadership
 Helping / Altruism

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Sexual Selection: Two Forms

Intrasexual Competition: members of
the same sex compete with each other
for sexual access to members of the
other sex
Male-male competition
 Female-Female competition

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Think about a same-sex friend.

In the past 3 months, how did your
friend compete with other same-sex
competitors for the attention of the
opposite-sex?
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Men (more than women)
He lifted weights.
Women (more than men)
She went on a diet to
improve her figure.
He had sex on the first date. She played hard to get.
He drove an expensive car. She shaved her legs.
He showed off his driving
She giggled when guys
skills.
were around.
He slept around with a lot of She learned how to apply
girls.
cosmetics.
He acted like he was
She was sympathetic to his
interested in sports.
troubles.
He mentioned that he had a She got a new, interesting
lot of status and prestige
hairstyle.
among his work colleagues.
He strutted in front of the
She wore stylish,
group.
fashionable clothing.
© 2015 M. Guthrie Yarwood
Sexual Selection: Two Forms
Intersexual Competition: members of
one sex choose a mate based on their
preferences for particular qualities in that
mate
The Office
 “Mate Preferences”

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Sexual Selection: Two Forms

What things do men look for in a female
mate?

What things do women look for in a
male mate?
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Mate Preferences
3
2
*
*
*
n.s.
1
0
Love v.
Status/Resources
Dependable/Stable vs. Education/Intelligence Sociability vs. Similar
Good Looks/Health
vs. Desire for
Religion
Home/Children
Men
Women
(Shackelford et al., 2005)
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Mate Preferences for Personality
Similarity

Genetic Similarity Theory
 Adaptation to prefer mates with similarity levels of specific
personality traits.

Social Exchange Theory
 Adaptation to prefer mates with same overall mate value.
 Matching Theory**

Female MZ and DZ twins
Ranked mate preferences; self-reported TIPI

Both were heritable

(Verweij et al., 2014; Phillips et al., 2010)
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2 Explanations for Individual
Differences

Frequency Dependence

Fluctuation Optimum
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Frequency Dependence
If level of
personality trait
is successful
If level of a
personality trait
is not successful
↑ in frequency
↓ in frequency
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Cheating
Strategy
Balance!
• Feigns cooperation,
then defects
As number of
psychopaths ↑,
↑ cost to
cooperative
humans
Benefit to
cheating
strategy ↓, so #
psychopaths ↓
More people
evolve cheatingdetector
mechanisms
↑ Cost to
psychopaths
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Fluctuating Optimum

Diversity in traits (high and low levels) exist
because:
 In certain places, a high level was advantageous
 In other places, a low level was advantageous
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China’s
Bachelors
Changes in
environment
Personality trait
leading to low
reproductive success
is least desirable trait
Determine level of
personality trait that
leads to high
reproductive success
Personality trait
leading to high
reproductive success
is more desirable trait
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Sex Differences in Personality

Video #1 Children and Altruism

Same adaptive problems – no sex
differences

Different adaptive problems – sex
differences!
 Men: Paternity Uncertainty
 Women: Commitment from Partner
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Big Five Trait
Men higher on:
Assertiveness; Aggressiveness;
Dominance (E)
Adaptive Problem?
Openness to Ideas
Women higher on:
Sociability (E)
Neuroticism
Agreeableness
Conscientiousness
Openness to Feelings
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Men higher in Aggression
Engage in more aggression
 More and longer homicidal thoughts
 More likely to be victims


Adaptive Problems include:
 Parental investment
 Intrasexual (male-male) Competition
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Murder: Byproduct or adaptation?

Byproduct Hypothesis (Kendrick & Sheet, 1993)
 Byproduct: neutral or bad characteristics associated
with an overall beneficial mutation.

Homicide Adaptation Theory (Buss & Duntley, 2006)
 Homicide solves an adaptive problem.
(CDC, 2002; Kenrick & Sheets,1993))
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Extraversion and Desire for
Sexual Variety

Less investment, more variety!
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Altruism and Inclusive Fitness

A.
B.
C.
D.
E.
You are on a large ship and the ship is
sinking. Time is running out! From first to
last, rank the order in which you will save
each person!
Your romantic partner
Your mother
Your child
Your sibling
Your friend
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Kin
Altruism
• Benefit to altruistic
individual comes from
fact that other individual
is likely to be his/her kin
Reciprocal
Altruism
• Benefit to altruistic
individual comes from
reciprocation of altruism
by other individual
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Altruism and Inclusive Fitness

Inclusive fitness theory (kin selection; Hamilton, 1964)

Coefficient of Relatedness (r)

r = proportion of alleles of person A that are
identical to alleles of person B
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Altruism: Hamilton’s Rule
An individual can be altruistic if c < b*r
 C = cost; b = benefit; r = relatedness


An individual may not reproduce in a given
year (c=1) to help her sibling if this helps the
sibling raise at least 5 additional offspring (r=
.25; b=5).
 1 < 5*.25 → 1< 1.25 √

Flipping equation around: If r = ½, then benefit, b, must ≥ 2c
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Altruism: Hamilton’s Rule

Austin and his wife do not reproduce in two
years (c=2). To help his brother, Austin is
thinking about raising two of his nephews.
Should Austin help his brother?
A. Yes!
 B. No!

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Altruism: Person-Situation Interaction

Strong Situations
 When will people typically help?
 When will people typically not help?

Weaker Situations
 Personality predicts helping
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Situation or Personality?

#1

#2

#3

Supermarket
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Kin or Reciprocal?
Self-Report Altruism Scale (SAR; Rushton, Chrisjohn, & Fekken, 1981)
I have helped push a stranger’s car out of the snow
I have given directions to a stranger
I have made change for a stranger
I have given money to a charity.
I have given money to a stranger who needed it (or asked me for it).
I have donated goods or clothes to a charity
I have done volunteer work for a charity
I have donated blood.
I have helped carry a stranger’s belongings (books, parcels, etc.).
I have delayed an elevator and held the door open for a stranger
I have allowed someone to go ahead of me in a lineup (at photocopy machine, in the
supermarket).
I have given a stranger a lift in my car.
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Fast, Life History Strategy
Narcissism
Excessive ego, selfish
Psychopathy
Machiavellianism
callous, impulsive,
predatory
calculated social
manipulation
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Can we be both prosocial and
antisocial?

Babies

Self-reported Altruism Scale and Measures of
delinquency
 r = -.08, n.s.

Altruism → Positive Emotionality

Antisocial → Negative Emotionality PLUS lack
of constraint (Low C)
(Krueger et al., 2001)
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Alternative Theories to Evolution

Social Role Theory

Measurement Error
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Limitations of Evolutionary
Psychology

We cannot go back in time to confirm
our hypothesis

Modern conditions are from ancestral
conditions

Gender differences are NOT VERY
LARGE
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