Lecture 5 PSYCH 290Outline of Last Lecture I. I. Critiques of the Five Factor ModelII. Broader Critique of Personalitya. Person-Situation DebateIII. Personality’s ResponseIV. Birth OrderV. Can Personality Change?a. Types of changeb. Rank-Order StabilityVI. Egos Inflating Over Time?Outline of Current Lecture I. Behavioral genetics of personalitya. What is heritability and how do we measure it?b. Genetic contributions to personalityc. Do parents matter?II. Evolutionary perspectives on personalitya. Human natureb. Individual differencesc. Sex differencesCurrent LectureGenetics, Evolution, and Personality Genetics and Personality-The nature-nurture “debate”-Which is more important: genes or environment?-How is personality shaped by genes?-How is personality shaped by the environment?Behavioral Genetics-Study of genetic and environmental contribution to behavior and personality-Aren’t just interested in the genetic part, they are also interested in the environment part-We share >99% of our genes with other humans (98% with chimpanzees!)-E.g. having two harms, two legs, eyes…Partitioning the Variance-Genes (Heritability)-Shared environment-Nonshared environment (+ error)-Birth order: being an older child you might have a different upbringing-Percent of variance that is genetic (ranges from 0-1)What does Heritability Tell Us Again?A. How likely a trait is to be genetically determinedB. How likely a trait is to be environmentally determinedC. The occurrence of a trait among twinsD. The percentage of variance in a trait that is due to genetic factorsE. The percentage of variance in a trait that is due to the nonshared enviornmentMeasuring Heritability-Twin Studies-Twins vary in genetic similarity-Monozygotic/identical twins share 100% of genes-Dizygotic/fraternal twins share about 50% of genes-But, twins share common environment-If we see differences between fraternal or identical twins, they must be from thegenetic if they have the same environment-Assumes shared environments are equal across twins-If genes matter, we would assume that identical twins would be more similar in personality than fraternal twins. But if genes don’t matter and environment does, there would not be a big difference.-Estimating Heritability from Twin Studies -Heritability (h) = 2x (rMZ –rDZ)-MZ = monozygotic DZ = dizygotic-h extraversion = 2 x (.45 -.20) = .50-Issues with Twin Studies-Identical twins may be treated differently than fraternal twins-Violates equal (shared) environments assumption-Twins in general may have unique experiences-Adoption studies-Are adopted children’s personalities more similar to biological or adoptive parents?-Are adoptive parents’ personalities more similar to biological or adopted children?-How similar are children’s personalities within a family?-Issues with Adoption Studies-Children are not randomly assigned to families (selective placement)-Adoptive families (and children) may differ from general population -It is random who adopts childrenQuestionAdopted children’s personalities are more similar to the personalities of their adoptive compared to biological parents?A. TrueB. False Important Facts About Heritability-Heritability estimates are strongly determined by particular group being studied.-So heritability estimates apply to groups, not individuals.-Estimates also vary according to assessment method-Heritability estimates are only as precise as measurements involved-Estimates tell us nothing about specific genes or environmental factors involved-Tell us “what” but not “why”QuestionTelevision watching is heritable.A. TrueB. FalseHeritability of Personality and Behavior-Personality traits: h is about .50-Big Five-Psychopathy-Narcissism-This explains a large portion, but you must remember there is still a large portion missing-Attitudes and behavior-Conservative values: h about .35-Divorce-Nonshared environment > shared environment-Shared environment doesn’t matter?! How can Behavior be Heritable?-Genes-Heritable traits-Neuroticism-Traditionalism-Impulsivity-Dominance-Behavior-Voting-Overeating-DivorceQuestionWhat is the heritability of optimism?.60 .30A. .15B. .30C. .60D. .90E. 1.00“The Nurture Assumption”-Challenged effects of parenting (shared environment)-Parenting studies don’t account for genes-Adoption studies show few parenting effects-Stressed nonshared environment -Peers, neighborhoods -Critical response from psychologists-How do we define environments?-Are any environments truly “shared”?-Not all siblings are raised the same way-Though siblings may go to the same school, they don’t necessarily have the same experience there -Gene-environment interactionsGene-Environment Interactions-Genes can predispose people to react differently to the same situation-Specific environments (e.g., child abuse) can “activate” or modify certain genes-Example-When does stress cause depression-847 children tested from age 3 to 26-Dunedin Multidisciplinary Health and Development Study-Interested in a specific gene that predisposed people to depression-Serotonin transporter gene (5-HTTLPR)-Has different combinations-Short/short (associated with vulnerability to depression)-Short/long (associated with vulnerability to depression)-Long/long-Assessed # of stressful life events < age 26-Were interested on the effects of stress on depression based on what allele you had-People who have the short/short allele reported having the most depression with high numbers of stressful life events according to S- and O-data Personality is (partially) Heritable-But which traits are inherited-Why?-How?-Where does variability in personality come from?Natural Selection-Charles Darwin-Most adaptive genes most likely are passed on to offspring-Important principles-Competition for limited resources-Random genetic variation-E.g. – some people are taller than others; some birds have different shaped beaks-Adaptation to the environment Survival of the Fittest-Darwin’s finches-Different and specialized beaks for the environments they live in-There has to be some sort of selection pressure to cause the evolution-These processes are depending on other environmental occurrencesEvolutionary Psychology-Emphasizes inherited, adaptive nature of behavior and mental processes-Adaptive traits-Increase an organism’s likelihood of survival and reproduction-Are more likely to be passed on to future generations-Huge time span, not just the past 100 years-Works