Download variance - Interpersonal Research Laboratory

Question
• Where did your personality come from?
• Random
• Environment
• Genetics
“Twin Study”
Monozygotic (MZ)
“identical”
Genetically identical
Dizygotic (DZ)
“Fraternal”
No more genetically related
than siblings
“Twin Study” Example
Give 100 MZ pairs a measure of
Extraversion
Calculate a correlation
r = .50
Give 100 DZ pairs a measure of
Extraversion
Calculate a correlation
r = .30
Twin Study
• Why is MZ > DZ?
• Heritability Coefficient
– The proportion of behavioral variance that can be
explained by genetic variance
• (MZr – DZr) x 2
• (.50 - .30) x 2 = .40
• Heritability of Extraversion = 40%
Behavior Genetics
• Note: Doesn’t really study behavior or
genetics directly
• Typical Heritability of personality traits is
around 40%
Behavior Genetics
• Genes matter!
• Heritability are almost always greater than
zero
• Not all of personality is determined by the
environment or random chance
Genes and Environment
• Environment can affect heritability
• Example:
– Height and food intake
Genes and Environment
• Genes work though the environment to
affect behavior
Genes and Environment
Genes gave him bad eyesight
Genes and Environment
Wearing glasses caused him to be teased and rejected by the opposite
sex
Genes and Environment
Due to these interaction he becomes introverted
Note: Introversion due in part to genes, but only came about through
environment
Genes and Environment
• Diathesis-Stress Model
• A genetic predisposition can cause a
person to develop maladaptive behaviors
in stressful situations
Diathesis-Stress
Genetic
Predisposition
No Genetic
Predisposition
Genetic
Predisposition
No Genetic
Predisposition
Diathesis-Stress
Genetic
Predisposition
No Genetic
Predisposition
Stressful Event Occurs
Genetic
Predisposition
No Genetic
Predisposition
No Stressful Event Occurs
Diathesis-Stress
Disorder
No Disorder
No Disorder
No Disorder
Behavior Genetics
• Limitations
• All humans are highly similar to each other
– Share 90% of genes
• BG is only looking at differences in the
remaining 10%
Behavior Genetics
• Limitations
• Saying “A father shares 50% of his genes with
his daughter” really means
• “A father shares 50% of the genetic material that
varies across individuals with his daughter”
• Heritability Coefficient
– The proportion of behavioral variance that can be
explained by genetic variance
Behavior Genetics
• Why do you have two feet?
– Environment?
– Genes?
• Heritability of arms would be zero!
Behavior Genetics
• Thus, if there is no variation due to genetic
influences heritability will be zero
• Why would some elements of our
personality and body not vary across
people?
• Important for survival!
Evolution
• Applied to human behavior:
• Behaviors are present because in the
evolutionary history of human species,
these behaviors were helpful or necessary
for survival.
– Survive
– Reproduce
Evolution
• Examines the shared 90% of genes
• Asks: How a behavior pattern could have
been adaptive during the development of
the human species
Evolution
• Not forward thinking
– e.g., giraffes neck
• Don’t want to consciously do this (we are
wired)
– Its not about what you consciously want, its
about what you ultimately try to do!
But I don’t want to have kids!
• You would not be here if SOMEONE didn’t have
children.
• What caused them to reproduce?
• Sexual urges (do you think you would be here
otherwise?)
• Your sexual urges are based on an inherited instinct
• Even if you don’t WANT to reproduce, your sexual urges
make it more likely that you WILL have children
• Other examples: pornography, etc.
Evolution
• Morality and evolution
• Naturalistic Fallacy
• If it is natural it is good
• e.g., you and kids
• Political objections are irrelevant from a
scientific standpoint
Evolution
• Works at the level of the GENE, not the
individual
• “You” really are not even important (or any
animal) in an evolutionary framework it is
all about the GENES!
– “The Selfish Gene”
• http://www.bgfl.org/bgfl/custom/resources_
ftp/client_ftp/ks1/maths/dice/
“The Blind Watch Maker”
• Someone finds a watch on the ground
(highly complex)
• Someone must have made it
• How can complex life result from random
chance (mutation) and simple selection
rules?
“The Blind Watch Maker”
• Group Activity
– Need:
• Blank paper
• Pen or pencil
• Straight edge
(1, 2)
(3, 4)
(5, 6)
How to play
• 1) Mark a small dot anywhere on the paper
• 2)Roll the die
• 3) Mark a second dot on the paper exactly half
way between your last dot and the vertex
indicated by the rolled dice (do not connect the
dots)
• 4) Repeat steps 2 and 3
http://www.shodor.org/MASTER/fra
ctal/software/Sierpinski.html
“The Blind Watch Maker”
• Product appears to be complex and
planned
• Only created with:
– 1) Random chance (die)
– 2) Simple rules (move halfway)
Evolutionary Psychology
• Relatively new field
• Identify a common behavior pattern
• Ask how it could have been adaptive
• Note: Examining “human nature”
• Research has tended to focus on
– Sex (mate selection and strategies)
– Aggression
Evolutionary Theory
• Please think of a serious committed
romantic relationship that you have had in
the past, that you currently have, or that
you would like to have. Imagine that you
discover that the person with whom you’ve
been seriously involved became interested
in someone else. What would distress or
upset you the more (only select one)
• A) Imagining your partner forming a deep
emotional attachment to that person
• B) Imagining you partner enjoying
passionate sexual intercourse with that
person
• A) Imagining your partner trying different
sexual positions with that person
• B) Imagining your partner falling in love
with that person
Reporting more distress about
sexual infidelity
100
80
60
40
20
0
Male
Female
Reporting more distress about
sexual infidelity
100
80
60
40
20
0
Male
Female
Physiological Responses
• Sexual Image
• . . . .Imagine your partner is having sexual
intercourse with this other person
• Emotional Image
• . . . .Imagine that your partner is falling in
lave and forming an emotional attachment
to that person
Physiological Responses
• Measured
• Electordermal activity
– Electrodes on hand (nervous)
• Pulse rate
• Electromyographic activity
– Brow (nervous)
6
EDA
Pulse
Brow
4
Sexual Image
2
0
-2
Emotional Image
-4
-6
Male
Female
Results
• Males tend to get more upset (physically
and self-report) with sexual infidelity
• Females tend to get more upset
(physically and self-report) with emotional
infidelity
• Why?
Evolutionary Psychology
• Reproductive success
• Note don’t make the errors of:
• “that’s not what I want”
• “that’s not moral so it must be incorrect”
Evolutionary Psychology
• Facts:
• 1) Females always know that their child is their
own
• 2) Males never completely sure of this
• 3) It takes more resources for a female to
produce a child than a male
Evolutionary Psychology
• Males most reproductively successful if they
have multiple mates
– It is “cheap” to reproduce
– Less cost associated with each offspring
• It is a waste of time to stay with one woman and
one set of children
– If he leaves they will probably survive
– If he leaves he can reproduce with another person
Evolutionary Psychology
• Females most reproductively successful if
they have one mate who helps provide
– More “costly” to reproduce
– More cost associated with each offspring
• If male stays
– Increases likelihood children will survive
– If children survive will reproduce in the future
Evolutionary Psychology
Women more sensitive to “emotional
infidelity” more likely to keep mate around
(and therefore more reproductively
successful)
Men more sensitive to “sexual infidelity”
more likely to avoid caring for offspring not
his own (and wasting resources)
Personal Ads
• I am very energetic,
have a great sense of
humor, honest,
thoughtful, romantic and
love to cook. I am
looking for someone who
is romantic, outgoing,
has a great sense of
humor and of course
likes kids and animals. If
you are out there maybe
we can get together and
talk.
Personal Ads
• I'm a very honest and
true person who is down
to earth. I'm sensitive
with a big heart yet
strong minded with lots
of ambition. I have a lot
of love inside to give to
the right person.I'm a
one man women who is
very faithful and
committed.
Personal Ads
• Because I am a
professional individual, I
don`t believe in dating at
the office to avoid
"politics and rumors."
Just got back into the
dating loop, (just brokeup) But, Just got a new
convertible! Want2go4 a
ride?
Personal Ads
• . . I enjoy dining out
occasionally, "in" is
where I prefer, hands
down. When you have a
pool table, air hockey,
swimming pool, jacuzzi,
and a karaoke "system"
(not machine) at your
disposal, you tend to be
content staying home for
the most part. I work
hard for what I have. . . .
Results
• Top 3 qualities men and women look for
• Intelligence
• Kindness
• Love
Results
• Women tend to seek: (Provider characteristics)
• Tall and strong
– 80% say they want a male over 6 feet
• Good earning potential
• Older males
Results
• Men tend to seek (Child bearing
characteristics):
• Younger women
• Attractive
– Full lips, clear and smooth skin, clear eyes,
lustrous hair, and good muscle tone
Why?
• Men and women seeking the same thing
– Greatest possible likelihood for successful
reproduction
• Women bear children
– Youth related to success (reproductive peak)
– Attractiveness related to successful reproduction
• e.g., lips, complexion, etc.
• Men's contribution is support
– Most men produce healthy sperm (regardless of age)
But. . .
Evolutionary Theory
• Why are some women attracted to highly
unstable but extremely attractive men?
• “Sexy Son Hypothesis”
• Different reproductive strategy
– Hope offspring will also be “sexy son”
• Mate with more women in the future