Evolutionary Perspectives on Personality. Part Two. Biological Domain Chapter 6: Do our genes...
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Transcript of Evolutionary Perspectives on Personality. Part Two. Biological Domain Chapter 6: Do our genes...
CHAPTER 8Evolutionary Perspectives on Personality
© 2015 M. Guthrie Yarwood 2
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 3
Lecture Outline 3 Ways personality became an adaptation
Natural Selection, 2 Types of Sexual Selection
2 Evolutionary Explanations for Individual DifferencesFluctuating Optimum, Frequency Dependence
Sex Differences in Personality
Altruism and Inclusive Fitness
© 2015 M. Guthrie Yarwood 4
Adaptation requirementsA 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 5
3 Ways Personality Traits Became Adaptations Natural Selection
Sexual SelectionIntrasexual CompetitionIntersexual Competition
© 2015 M. Guthrie Yarwood 6
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.
© 2015 M. Guthrie Yarwood 7
Natural Selection
Problematic Mutations
↓ Production /
Death
Removed from
population
Beneficial Mutations
↑ Production / Survival
Slowly Spreads through
populationAdaptation
Personality Traits as Adaptations: What adaptive problems do the Big Five solve?
•High vs. Low
O
•High vs. Low
C
•High vs. Low
E
•High vs. Low
A
•High vs. Low
N
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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
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
© 2015 M. Guthrie Yarwood 10
© 2015 M. Guthrie Yarwood 11
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?
© 2015 M. Guthrie Yarwood
Men (more than women) Women (more than men)
He lifted weights. 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 skills.
She giggled when guys were around.
He slept around with a lot of girls.
She learned how to apply cosmetics.
He acted like he was interested in sports.
She was sympathetic to his troubles.
He mentioned that he had a lot of status and prestige among his work colleagues.
She got a new, interesting hairstyle.
He strutted in front of the group.
She wore stylish, fashionable clothing.
Sexual Selection: Two Forms Intersexual Competition: members of
one sex choose a mate based on their preferences for particular qualities in that mate
“Mate Preferences”
© 2015 M. Guthrie Yarwood 13
The Office
© 2015 M. Guthrie Yarwood 14
Sexual Selection: Two Forms What things do men look for in a female
mate?
What things do women look for in a male mate?
© 2015 M. Guthrie Yarwood 15
0
1
2
3
Mate Preferences
Men Women
*n.s.
**
(Shackelford et al., 2005)
© 2015 M. Guthrie Yarwood 16
Mate Preferences for Personality Similarity Genetic Similarity Theory
Adaptation to prefer mates with similarity levels of specific personality traits.
Social Exchange TheoryAdaptation 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)
© 2015 M. Guthrie Yarwood 17
2 Explanations for Individual Differences Frequency Dependence
Fluctuation Optimum
18© 2015 M. Guthrie Yarwood
If level of personality trait is successful
↑ in frequency
If level of a personality trait is not successful
↓ in frequency
Frequency Dependence
© 2015 M. Guthrie Yarwood 19
Cheating Strategy• Feigns cooperation,
then defects
As number of psychopaths ↑,
↑ cost to cooperative
humans
More people evolve cheating-
detector mechanisms
↑ Cost to psychopaths
Benefit to cheating
strategy ↓, so # psychopaths ↓
Balance!
© 2015 M. Guthrie Yarwood 20
Fluctuating Optimum
Diversity in traits (high and low levels) exist because:In certain places, a high level was advantageousIn other places, a low level was advantageous
© 2015 M. Guthrie Yarwood 21
Changes in environment
Determine level of personality trait that
leads to high reproductive success
Personality trait leading to high
reproductive success is more desirable trait
Personality trait leading to low
reproductive success is least desirable trait
China’s Bachelors
Sex Differences in Personality
Video #1 Children and Altruism
Same adaptive problems – no sex differences
Different adaptive problems – sex differences! Men: Paternity UncertaintyWomen: Commitment from Partner
© 2015 M. Guthrie Yarwood 22
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Big Five Trait Adaptive Problem?
Men higher on:
Assertiveness; Aggressiveness; Dominance (E)
Openness to Ideas
Women higher on:
Sociability (E)
Neuroticism
Agreeableness
Conscientiousness
Openness to Feelings
© 2015 M. Guthrie Yarwood 24
Men higher in Aggression Engage in more aggression More and longer homicidal thoughts More likely to be victims
Adaptive Problems include:Parental investmentIntrasexual (male-male) Competition
© 2015 M. Guthrie Yarwood 25
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))
© 2015 M. Guthrie Yarwood 26
Extraversion and Desire for Sexual Variety Less investment, more variety!
© 2015 M. Guthrie Yarwood 27
Altruism and Inclusive Fitness 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!
A. Your romantic partner
B. Your mother
C. Your child
D. Your sibling
E. Your friend
© 2015 M. Guthrie Yarwood 28
•Benefit to altruistic individual comes from fact that other individual is likely to be his/her kin
Kin Altruism
•Benefit to altruistic individual comes from reciprocation of altruism by other individual
Reciprocal Altruism
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
© 2015 M. Guthrie Yarwood 29
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
© 2015 M. Guthrie Yarwood 30
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!
© 2015 M. Guthrie Yarwood 31
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Altruism: Person-Situation Interaction Strong Situations
When will people typically help?When will people typically not help?
Weaker SituationsPersonality predicts helping
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Situation or Personality?
#1
#2
#3
Supermarket
35© 2015 M. Guthrie Yarwood
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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NarcissismExcessive ego, selfish
Machiavellianismcalculated social
manipulation
Psychopathycallous, impulsive,
predatory
Fast, Life History Strategy
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Can we be both prosocial and antisocial? Babies
Self-reported Altruism Scale and Measures of delinquencyr = -.08, n.s.
Altruism → Positive Emotionality
Antisocial → Negative Emotionality PLUS lack of constraint (Low C)
(Krueger et al., 2001)
© 2015 M. Guthrie Yarwood 38
Alternative Theories to Evolution
Social Role Theory
Measurement Error
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
© 2015 M. Guthrie Yarwood 39