Chapter Six Genetics Evolution and Personality Basic Approach

Chapter Six 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 Pairs Genetically identical Dizygotic Pairs Not identical Correlation. MZ Correlation. DZ Difference x 2 = HERITABILITY – Adoption Studies: How adopted children resemble… Biological Parents Genetically related Correlation. BP Adopted Parents Not related > Suggests a genetic component Correlation. AP

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 Temperaments Neuroticism Emotionality Extraversion Activity Agreeableness. Sociability Openness Impulsivity (-) 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 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

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 Females Males • 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: Females Males • Family support • Paternity Jealousy results from: Females Males • 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