Evolutionary Perspectives on Personality. Part Two. Biological Domain Chapter 6: Do our genes...

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CHAPTER 8Evolutionary 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)?

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

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

3 Ways Personality Traits Became Adaptations Natural Selection

Sexual SelectionIntrasexual CompetitionIntersexual Competition

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.

Natural Selection

Problematic Mutations

↓ Production /

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

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

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?

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”

The Office

Sexual Selection: Two Forms What things do men look for in a female

What things do women look for in a male mate?

Mate Preferences

Men Women

(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 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)

2 Explanations for Individual Differences Frequency Dependence

Fluctuation Optimum

If level of personality trait is successful

↑ in frequency

If level of a personality trait is not successful

↓ in frequency

Frequency Dependence

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!

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

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

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

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

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))

Extraversion and Desire for Sexual Variety Less investment, more variety!

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

•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

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

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!

Altruism: Person-Situation Interaction Strong Situations

When will people typically help?When will people typically not help?

Weaker SituationsPersonality predicts helping

Situation or Personality?

Supermarket

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.

NarcissismExcessive ego, selfish

Machiavellianismcalculated social

manipulation

Psychopathycallous, impulsive,

predatory

Fast, Life History Strategy

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)

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

Evolutionary Perspectives on Personality. Part Two. Biological Domain Chapter 6: Do our genes...

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