Chapter 9 The Inheritance of Personality Behavioral Genetics

Chapter 9 The Inheritance of Personality: Behavioral Genetics and Evolutionary Psychology Lecture Slides created by Tera D. Letzring Idaho State University © 2016 W. W. Norton & Company, Inc. © 2013 W. W. Norton & Company, Inc.

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 ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 1

Behavioral Genetics • Addresses 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 ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 2

Behavioral Genetics: Calculating Heritability • 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) versus dizygotic (DZ) twins – Assumption ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 3

Behavioral Genetics: Calculating Heritability • Heritability coefficient Identical (MZ) Fraternal (DZ) Score of First Twin Score of Second Twin Pair 1 54 53 52 49 Pair 2 41 40 41 53 Pair 3 49 51 49 52 . . . . r-. 60 r -. 40 . . . ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. Fraternal (DZ) 4

Behavioral Genetics: Calculating Heritabilities • Heritability coefficients from twin studies ≈. 40 • Heritability coefficients from non-twin studies ≈. 20 • Difference suggests that the effects of genes are interactive and multiplicative ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 5

Behavior Genetics: What Heritability Tells You • Genes matter • Insight into the effects of the environment on personality development – Shared family environment does not seem to matter very much ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 6

Behavior Genetics: What Heritability Tells You Does the family matter? • No or very little – Extreme conclusion – Behavioral genetics studies on the effect of shared family environment – Research with selfreports ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. • Yes – Developmental psychology – Behavioral observation 7

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 siblings turned out? ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 8

Behavior Genetics: What Heritability Can’t Tell You • Nature versus 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 • HOW genes affect personality – Create propensities to behave in certain ways ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 9

Behavior Genetics: Molecular Genetics • Uses the methods of molecular biology • DRD 4 affects dopamine receptors • 5 -HTT gene affects serotonin – Alleles and cultural differences • Limitations: not applicable to everyone ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 10

Behavior Genetics: Gene-Environment Interactions • Genes are not causal • There must be an environment in order for there to be behavior • Environments can affect heritabilities • Genetic expression and social environment • Choice of environments (niche picking) • People can react differently to the same environment ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 11

Behavior Genetics • Epigenetics: experience affects biology – May be possible to help people find environments that will lead to good outcomes • The future – Genes have important influences on personality – Researchers are working to find out which genes are dependably associated with personality – The big picture will be complicated ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 12

Evolutionary Personality Psychology • Addresses how patterns of behavior that characterize all humans may have originated in the survival value of these characteristics • Evolution and behavior – Assumption – Identify common behavior patterns and then determine how the behavior was adaptive ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 13

Evolutionary Personality Psychology: Evolution and Behavior • Aggression and altruism • Self-esteem: sociometer theory • Depression ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 14

Evolutionary Personality Psychology: Evolution and Behavior • Mating behavior – Mate selection – Mating

Evolutionary Personality Psychology: Evolution and Behavior • Mating behavior: Attraction – 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 ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 16

Evolutionary Personality Psychology: Evolution and Behavior • Mating behavior: Attraction – Some complications • Women who are too thin cannot bear children • Larger women used to be considered ideal • Attraction is influenced by more than physical characteristics • Male physical attractiveness is more important to women than it should be • Culture matters ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 17

Evolutionary Personality Psychology: Evolution and Behavior • Mating behavior: Strategies – Differences between men and women • Explained in terms of reproductive success – Some similarities ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 18

Evolutionary Personality Psychology: Evolution and Behavior • Mating behavior: Sociosexuality – Men are generally higher – Implications of high versus low levels ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 19

Evolutionary Personality Psychology: Evolution and Behavior • Mating behavior: Jealousy – Gender difference in the experience of jealousy – Sexy son hypothesis ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 20

Evolutionary Personality Psychology: Individual Differences • Focus has been on general human nature • Adaptation – Diversity is necessary for adaptation • Accounting for individual differences – Behavioral patterns evolved as reactions to particular environmental experiences – Several possible behavioral strategies evolved – Some behaviors may be frequency dependent • Human nature is flexible ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 21

Evolutionary Personality Psychology: 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 ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 22

Evolutionary Personality Psychology: Objections and Responses 4. Human flexibility – Response 5. Biological determinism or social structure? – Aspects of social structure – Theoretical importance – Practical importance ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 23

Changes in Educational and Income Differences Between Husbands and Wives ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. Share of husbands whose wives’ income top theirs in 1970 Share of husbands whose wives’ income top theirs in 2007 4% 22% 24

Will Biology Replace Psychology? • Implication that personality is rooted in biology • Biological reductionism • We do not know enough about biology • Biology leaves out most of psychology and does not ask many important psychological questions ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 25

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. ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 26

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. ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 27

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 theory. c) places too much emphasis on how social structure influences behavior. d) does not explain how people living now decide to behave. ©© 2016 W. W. Norton & Company, Inc. 2013 W. W. Norton & Company, Inc. 28