PSY 239 401 Chapter 9 SLIDES

Chapter 9:
The Inheritance of Personality:
Behavioral Genetics and Evolutionary
Theory
The Personality Puzzle
Sixth Edition
by David C. Funder

Slides created by
Tera D. Letzring
Idaho State University
© 2013 W. W. Norton & Company, Inc.

1

Objectives
• Discuss two biologically based approaches to
how personality might be inherited
• Discuss how these approaches can be
combined with each other and with other
approaches

2

Behavioral Genetics
• Attempts to explain how personality traits that
differ among individuals are passed from
parent to child and shared by biological
relatives
• Examines how genes influence broad patterns
of behavior
• Controversy from associations with eugenics
and cloning
– Modern research is not concerned with these
issues.
3

Behavioral Genetics:
Calculating Heritabilities
• To examine how phenotypes may be
attributed to variation in genotypes
• Compare similarity in personality between
people who are and are not related and
people who are related to different degrees
– Monozygotic (MZ) vs. dizygotic (DZ) twins
– Assumption

4

• Heritability coefficient

5

6

• Heritability coefficients from non-twin studies
≈ .20
– Suggests that the effects of genes are interactive
and multiplicative

7

Behavior Genetics: What
Heritabilities Tell You
• Genes matter
• Etiology of disorders
• Insight into the effects of the environment on
personality development
– Shared family environment does not seem to
matter very much

8

Behavior Genetics: What
Heritabilities Tell You
Does the family matter?
• No or very little
– Extreme conclusion
– Behavioral genetics
studies on the effect
of shared family
environment
– Research with
self-reports

• Yes
– Developmental
psychology
– Effects of parent
training
– Based on technical
issues
– Based on behavioral
observation
9

Think About It
• If you have siblings, was the family
environment in which you grew up the same
as, or different from, theirs? If different, do
these variations account for differences in
how you and your sibling turned out?

10

Behavior Genetics:
Nature and Nurture
• Traits with little variation will have
heritabilities close to zero.
• You can’t use heritability to determine what
percent of a trait is determined by genetics
and by the environment.

11

Behavior Genetics: How Genes Affect
Personality
• Create propensities to behave in certain ways
• Molecular genetics
– Association method
– Homosexuality, behavioral and emotional control,
neuroticism and depression (cultural difference)
– Limitations: not applicable to everyone

12

Personality
• Gene-environment interactions
– There must be an environment in order for there
to be behavior
– Genes are not causal
– Next step
– Environments can affect heritabilities
– Genetic expression and social environment

13

Personality
• Gene-environment interactions
– Choice of environment to be consistent with
genetic tendencies
– The same environment can affect different
individuals in different ways
– Environments can determine how or whether a
gene is expressed
– Epigenetics
14

Behavior Genetics: The Future
• The fact that genes are important
determinants of personality is already wellestablished
• Researchers are working to find out which
genes are associated with personality

15

Evolutionary Personality Psychology
• Attempts to explain how patterns of behavior
that characterize all humans originated in the
survival value of these characteristics
• Evolution and behavior
• Identify common behavior patterns and then
determine how the behavior was adaptive

16

Evolutionary Personality Psychology:
Evolution and Behavior
• Aggression and altruism
• Self-esteem
• Depression

17

• Mate selection
– Men place higher value on physical attractiveness
and prefer younger mates
– Women place higher value on economic security
and prefer older mates
– Both want the highest likelihood of healthy
offspring who will survive and reproduce

18

• Mate selection: some complications
– Women who are too thin cannot bear children
– Larger women used to be considered to be ideal
– Attraction is influenced by more than physical
characteristics
– Male physical attractiveness is more important to
women than it should be

19

20

• Mating strategies
– Differences between men and women
– Sociosexuality
– Jealousy
• Sexy son hypothesis

21

Individual Differences
• Focus has been on general human nature
• Evolutionary reasons for individual differences
– Diversity is necessary for viability
– Behavioral patterns evolved as reactions to
particular environmental experiences
– Several possible behavioral strategies evolved
– Some behaviors may be frequency dependent

• Human nature is flexible
22

Stress Tests
1. Methodology: Backward speculation is
difficult to test empirically.
– Responses

2. Reproductive instinct
– Response: People do not have to consciously try
to do what is evolutionarily adaptive.

3. Conservatism
– Responses
23

Objections and Responses
4. Human flexibility
– Response

5. Gender differences are the result of social
structure.
– Aspects of social structure
– Theoretical importance
– Practical importance

24

Changes in Educational and Income
Diff erences Between Husbands and
Wives

25

Will Biology Replace Psychology?
• Biological reductionism
• We do not know enough about biology.
• Biology leaves out most of psychology and
does not ask many important psychological
questions.

26

Think About It
• When scientists learn that a particular brain
structure or chemical is associated with a personality
trait, how is that knowledge valuable? Does it help us
understand the trait better? Does it have practical
implications?
• If you are a woman, would you be comfortable
marrying a man who had less education and made
less money than you? If you are a man, would you be
comfortable marrying a woman who had more
education and made more money than you? Why?
Are these attitudes changing?
27

Clicker Question #1
Genes affect behavior
a)directly, by being able to control certain
behaviors.
b)because genes and behavior have a one-toone correspondence.
c)by influencing the propensities or tendencies
toward certain behaviors.
d)much more than does the environment.
28

Clicker Question #2
According to evolutionary personality psychology,
a)one way to explain personality and behavior is
to look at how behaviors might have been
adaptive for our ancestors.
b)personality is entirely determined by genetics.
c)everyone should have the same personality, and
those who differ are maladaptive.
d)evolutionary theory can only be used to explain
a few human behaviors.
29

Clicker Question #3
One criticism of evolutionary personality theory
is that it
a)attempts to explain only a narrow range of
behavioral patterns.
b)is too easy to find evidence against the theory.
c)places too much emphasis on how social
structure influences behavior.
d)does not explain how people living now decide
to behave.
30

PSY 239 401 Chapter 9 SLIDES

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