Chapter Six Genetics, Evolution, and Personality Genetics, Evolution, and Personality

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

Behavioral Genetics Key Methodologies –Twin Studies: Monozygotic PairsDizygotic Pairs Genetically identical Not identical Correlation MZ Correlation DZ Difference x 2 = HERITABILITY –Adoption Studies: How adopted children resemble… Biological ParentsAdopted Parents Genetically related Not related Correlation BP > Correlation AP Suggests a genetic component

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

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

Temperaments and the Big Five Big FiveTemperaments NeuroticismEmotionality ExtraversionActivity AgreeablenessSociability OpennessImpulsivity Conscientiousness Intelligence (-)

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?

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

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

Sociobiology 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 Study of the biological basis of human social behavior

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

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

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

Other Gender Differences 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

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”)

Assessment Little focus from behavioral genetics Assessment from genes unlikely –Behavior probably involves many genes –Ethical implications?

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

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