Genetics, Evolution, and Personality: The Biological Basis of Human Behavior

1. Chapter Six Genetics, Evolution, and Personality

2. Basic Approach of Biological Perspectives • Personality is genetically determined • Human behavioral tendencies arise from evolutionary processes • Human behavior is the product of a complex biological organism • Underlying genetics and biology influence processes in personality

3. Behavioral Genetics • Key Methodologies • Twin Studies: Monozygotic PairsDizygotic Pairs Genetically identical Not identical CorrelationMZ CorrelationDZ Difference x 2 = HERITABILITY • Adoption Studies: How adopted children resemble… Biological ParentsAdopted Parents Genetically related Not related CorrelationBP >CorrelationAP Suggests a genetic component

4. Temperaments Inherited personality traits present at birth • Genetically based • Pervasive—affect how and what people do • Three fundamental temperaments • Activity level—overall output of behavior • Sociability—preference for being with others • Emotionality—ease of being emotionally aroused • More recent views of temperaments • Approach and avoidance • Effortful control

5. Inheritance of Traits • Evidence of heritability for a broad range of traits • Evidence for genetic component for all of the “big five” personality traits

6. Temperaments and the Big Five Big FiveTemperaments Neuroticism Emotionality Extraversion Activity Agreeableness Sociability Openness Impulsivity Conscientiousness Intelligence (-)

7. Other Effects of Genetics • Genetics work through personality to effect: • Risk for divorce • Experiencing a serious life event • Levels of social support • Peoples attitudes on various topics • Important question: Are the effects of personality and genetics distinct?

8. Molecular Genetics • Much of human genome does not vary from person to person • Differences arise at locations where patterns of DNA proteins vary • Research has identified a gene location that relates to: • Novelty seeking • Reward pursuit • Impulse vs. constraint

9. Environmental Influences • Environmental effects may be underestimated • Judged as that which is not explained by genetics • Some environmental and genetic effects may have shared influence on an outcome (e.g., intelligence) • If shared variance is attributed to genetics, the environmental effect is underestimated • Environmental influences on personality operate primarily at the individual level • Sources of non-shared environmental influences • Peer, friends, social networks • Complementary, but diverging, roles within families • Parental preference

10. Sociobiology Study of the biological basis of human social behavior • Social behaviors exist because they confer adaptive advantage • Example: Altruism • May confer a biological disadvantage at an individual level • May help others in the same gene pool survive and reproduce (inclusive fitness) • Predicts altruism to members of kinship group • May form the evolutionary basis of cooperation

11. Genetic Similarity Theory • An extension of the concept of altruism • We are more attracted to strangers who genetically resemble us • Evidence? • Sexually involved couples shared more genetic markers than randomly selected couples • Couples with children shared more genetic markers than those without • Male friend pairs share more markers than random pairs • How detected? • Similar facial, physical features • Odor • Cultural similarities

12. Mate Selection and Competition FemalesMales • Greater investment in offspring • Less investment in offspring • Generate fewer offspring • Can generate more offspring • Choosier in mate selection • Less discriminating • Wait for best male • Maximize sexual opportunities • Males = success objects • Females = sex objects • Attract males with: • Attract females with: Fertility, youth, fitness, beauty Wealth, power, status

13. Jealousy Concerns according to evolutionary theory: FemalesMales •Family support • Paternity Jealousy results from: FemalesMales •Emotional bonds • Sexual infidelity

14. Females: Maximize attractiveness Strategy used more if husband has high income Males: Spend money Give in to wishes Strategies used more if wife is young or attractive Other Gender Differences

15. Young Male Syndrome • May have evolutionary roots • Manifest by posturing, risk behavior, or violence in response to sexual selection pressure • Elicited by specific situations • Single, unemployed, low-status (poor mating potential) • Evidence • Males more likely to commit murder • Men in prime mating age commit more murders • Most killings over status (“face”)

16. Assessment • Little focus from behavioral genetics • Assessment from genes unlikely • Behavior probably involves many genes • Ethical implications?

17. Behavior Genetics and Disorder • Schizophrenia • Rate of concordance in twins • MZ = 50% • DZ = 9% • Bipolar Disorder • Twin research suggests genetic contribution • Possible links to specific chromosomes (in Amish) • Alcohol Abuse • Possible link to gene for dopamine • Antisocial Behavior • Higher concordance rates among MZ twins on childhood behavior problems and adult crime

18. Another View of Behavior Problems • Premise: Two evolutionary processes influence behavior • Biological evolution—slow • Cultural evolution—much faster • Problems arise when the behavioral tendency from biological evolution conflicts with current cultural environment