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 Yarwood2

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 Yarwood3

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 4© 2015 M. Guthrie Yarwood

3 Ways Personality Traits Became Adaptations  Natural Selection  Sexual Selection Intrasexual Competition Intersexual Competition © 2015 M. Guthrie Yarwood5

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. 6© 2015 M. Guthrie Yarwood

Natural Selection Problematic Mutations ↓ Production / Death Removed from population Beneficial Mutations ↑ Production / Survival Slowly Spreads through population Adaptation 7© 2015 M. Guthrie Yarwood

Personality Traits as Adaptations: What adaptive problems do the Big Five solve? High vs. Low O C E A N © 2015 M. Guthrie Yarwood8

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 © 2015 M. Guthrie Yarwood9

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 Yarwood10

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 Yarwood11

© 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 Yarwood13 The Office

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 Yarwood14

© 2015 M. Guthrie Yarwood15 * n.s. * * (Shackelford et al., 2005)

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 © 2015 M. Guthrie Yarwood16 (Verweij et al., 2014; Phillips et al., 2010)

2 Explanations for Individual Differences  Frequency Dependence  Fluctuation Optimum © 2015 M. Guthrie Yarwood17

If level of personality trait is successful ↑ in frequency If level of a personality trait is not successful ↓ in frequency Frequency Dependence 18© 2015 M. Guthrie Yarwood

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! 19© 2015 M. Guthrie Yarwood

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 20© 2015 M. Guthrie Yarwood

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 21© 2015 M. Guthrie Yarwood China’s Bachelors

Sex Differences in Personality  Video #1 Children and Altruism Video #1 Children and Altruism  Same adaptive problems – no sex differences  Different adaptive problems – sex differences! Men: Paternity Uncertainty Women: Commitment from Partner © 2015 M. Guthrie Yarwood22

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 Yarwood23

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 © 2015 M. Guthrie Yarwood24

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. © 2015 M. Guthrie Yarwood25 (CDC, 2002; Kenrick & Sheets,1993))

Extraversion and Desire for Sexual Variety  Less investment, more variety! © 2015 M. Guthrie Yarwood26

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 27© 2015 M. Guthrie Yarwood

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 28© 2015 M. Guthrie Yarwood

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 Yarwood29

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 Yarwood30

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 Yarwood31

Altruism: Person-Situation Interaction  Strong Situations When will people typically help? When will people typically not help?  Weaker Situations Personality predicts helping © 2015 M. Guthrie Yarwood32

© 2015 M. Guthrie Yarwood33

Situation or Personality?  #1 #1  #2 #2  #3 #3  Supermarket Supermarket © 2015 M. Guthrie Yarwood34

Kin or Reciprocal? 35© 2015 M. Guthrie Yarwood 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.

© 2015 M. Guthrie Yarwood36 Narcissism Excessive ego, selfish Machiavellianism calculated social manipulation Psychopathy callous, impulsive, predatory Fast, Life History Strategy

Can we be both prosocial and antisocial?  Babies 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) © 2015 M. Guthrie Yarwood37 (Krueger et al., 2001)

Alternative Theories to Evolution  Social Role Theory  Measurement Error © 2015 M. Guthrie Yarwood38

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 Yarwood39