1. OVERVIEW The “nature-nurture” debate Evidence for nature –Heritability –Biological processes Evidence for nurture Nature and nurture interactions

2. THE “NATURE-NURTURE” DEBATE A devil, a born devil, on whose nature Nurture can never stick; on whom my pains Humanely taken, all, all lost, quite lost -The Tempest

3. THE “NATURE-NURTURE” DEBATE The simple view PRESENT BEHAVIOR = GENES + ENVIRONMENT The realistic view PRESENT BEHAVIOR = GENES + NUTRITION + PRENATAL ENVIRONMENT + CULTURE + PARENTAL PRACTICES + FAMILY INCOME + BIRTH ORDER + SCHOOLING + TRAUMAS + LUCK + …

4. EVIDENCE FOR NATURE: HERITABILITY Different ways of estimating genetic influence: Twin studies Relative studies Adoption studies Restriction fragment length polymorphisms (RFLP’s) Experimental animal studies

5. EVIDENCE FOR NATURE: HERITABILITY Heritability is an estimate of what percentage of the difference found overall between people in the same environment with different genes can be accounted for by their genes (as opposed to the influence of environment) Environment Genes Environment Fraternal Twins or Identical Twins Reared Apart Identical Twins

6. EVIDENCE FOR NATURE: HERITABILITY HERITABILITY IS NOT The chance that an individual will have a certain characteristic How much influence genes or environment have on an individual person The absolute influence of a gene outside the particular environment in which the estimate was made

7. EVIDENCE FOR NATURE: HERITABILITY Some results from the major twin studies: Intelligence – H = 30% - 70% (some specific cognitive abilities are more heritable than others) Activity level, emotional reactivity, sociability-shyness – H = 20% - 50% Neuroticism, extraversion, impulsivity, monotony avoidance – H = 23% - 45% Depression – 13% for male relatives and 30% for female relatives Vocational interests – r=0.43 twins reared apart Religiosity – r=0.49 twins reared apart, H = 50% Traditionalism – r=0.53 twins reared apart Attitudes toward drinking alcohol – H = 51% Television viewing time among young children Radicalism and toughmindedness – H > 50% Aggressive, antisocial, criminal behavior – H about 50%

8. EVIDENCE FOR NATURE: HERITABILITY Schizophrenia and Heritability 30% concordance IT and 6% concordance FT Gene linkage to chromosome 5 found but not replicated Percentage of children S: 1%3% 9%17% Not SS S Adopted Family Biological Family

9. EVIDENCE FOR NATURE: HERITABILTIY Be aware: There are not single genes for personality traits – most behavioral traits appear to be influenced by many genes, each with small effects. Flaws in adoption studies: children are not randomly assigned, often well-matched by adoption agencies, even relatives, often in very similar environment (i.e., Swedish culture is relatively homogenous). Twins reared apart are very hard to find.

10. EVIDENCE FOR NATURE: NEUROANATOMY Neuroanatomy: The Amygdala Aggressive behavior –Animals with rabies –Animals and people with epileptic focus in this area –Removal of amygdala usually leads to placidity, tameness Fear –People with Urback-Wiethe disease don’t experience or recognize fear –Monkeys with Kluver-Bucy syndrome lose fear and inhibition –Essential for classical conditioning (punishment and reward) –Activated during startle response

11. EVIDENCE FOR NATURE: BIOCHEMISTRY Testosterone Men vs. women Men at stage with testosterone is highest Violent activities and crimes by men at same age Rape and murder vs. burglary and drug offense The effects of testosterone are real, but weak.

12. EVIDENCE FOR NATURE: BIOCHEMISTRY Serotonin –Aggressive behavior –Depression GABA –Main inhibitory transmitter in the amygdala –Anti-anxiety drugs, such as barbiturates and benzodiazepines disinhibit GABA

13. EVIDENCE FOR NATURE: HEMISPHERE ACTIVATION Left Hemisphere Approach-related emotion Arousal -> happiness, resilience in the face of stress Underarousal -> vulnerable to sadness and depression Right Hemisphere Withdrawal-related emotion Arousal -> fear, disgust, anxiety Underarousal -> relaxation

14. EVIDENCE FOR NATURE: HEMISPHERE ACTIVATION Davidson’s Evidence from EEG Reliable from one month to another (r =.66) More right-sided activation and more intense negative and less intense positive trait mood More right-sided activation and more intense negative affect in response to film clips meant to elicit fear and disgust Infants who cried when separated from their mothers had higher right-sided activation Inhibited toddlers had low left-sided activation People with greater left-sided activation had more natural killer cell activity

15. I will describe to you a situation. Imagine the situation as vividly as you can. Picture the event happening to you. Try to imagine all the details of the situation. Picture in your “mind’s eye” the surroundings as clearly as possible. See the people or objects; hear the sounds; experience the event happing to you. Think the thoughts you would actually think in this situation. Feel the same feelings you would feel in this situation. Let yourself react as if you were actually there. You will have four minutes Imagine yourself winning $50,000 in a lottery and then taking a vacation in Hawaii.

16. EVIDENCE FOR NATURE: EMOTIONAL REACTIVITY Emotional Reactivity: E and Positive, N and Negative Larsen & Ketelaar (1991) Using mood induction procedure, they found the following correlations: InductionExtraversionNeuroticism Positive PA0.3-0.2 NA00 Negative PA00 NA-0.20.3 Neutral PA00 NA00.3 Gross, Sutton, & Ketelaar (1998) But maybe it’s baseline mood? Still found similar result with reactivity to film clips

17. EVIDENCE FOR NATURE: INHIBITED TO THE UNFAMILIAR Inhibited and Uninhibited to the Unfamiliar (Kagan) Infants observed at 4 months, put into groups –H: high movement, high crying –L: low movement, low crying Observed again at 9, 14, and 21 months –Most Group H infants were significantly more fearful than Group L infants at all three times

18. EVIDENCE FOR NURTURE: ATTACHMENT STYLES Secure –Mother was sensitive and responsive to child's signals –Love as trust, friendship, positive emotion Anxious/ambivalent –Mother was slow or inconsistent in responding to infant's cries –Love as preoccupying, almost painfully exciting struggle to merge with another person Avoidant –Mother consistently rebuffed the infant's attempts to establish physical contact –Love as fear of closeness and lack of trust

19. EVIDENCE FOR NURTURE: BIRTH ORDER Birth Order (Sulloway) Niches by birth order Birth order environment –Firstborns are bigger, have more status, have more knowledge –Competition between siblings for parents' attention –Niche to maximize attention they receive

20. EVIDENCE FOR NURTURE: BIRTH ORDER PERSONALITY PROFILES Firstborns –Identify with the parents more, tend to have more responsibility –Conservative, conscientious, self-confident, assertive, jealous, moralistic, inflexible, violent, cruel –Suddam Hussein, Cain, a high proportion of US presidents Laterborns –Spend their childhoods finding niches other than the one "already staked out by the parent-identified firstborn." –Sociable, agreeable, open to novelty and innovation, flexible and able to compromise –Joan of Arc, Thomas Jefferson, a high proportion of revolutionaries and rebels

21. EVIDENCE FOR NURTURE: GROUP SOCIALIZATION THEORY Harris’s Group Socialization Theory Strong claim: parents don't matter, development is all about peer groups Weak claim: peer groups have a strong influence on development

22. EVIDENCE FOR NURTURE: GROUP SOCIALIZATION THEORY Basic Phenomena of Group Behavior In-group favoritism Out-group hostility Between-group contrast Within-group assimilation Within-group differentiation

23. NATURE AND NURTURE INTERACTIONS A Central Theme in Personality and Social Psychology The dynamic interaction between the person and the situation. People come into the world with some predispositions. They act in accordance with these predispositions and get reactions and feedback from the environment. These reactions and feedback, in turn, inform, drive, and even determine their behavior in the future. The cycle continues.

24. NATURE AND NURTURE INTERACTIONS Diathesis-Stress Model Examples Schizophrenia (genetic diathesis) Phobias (environmental diathesis) Alcoholism (possible genetic/environmental) Depression (possible genetic/environmental) Stress Level Time Critical Point Patient Becomes Ill

25. NATURE AND NURTURE INTERACTIONS Continuity of Behavior: Two Hypotheses (Caspi, Bem, & Elder, 1987) The data on children who tantrum: Men: downward occupational mobility, erratic work lives, more likely to divorce Women: married men with lower occupational status, more likely to divorce, ill-tempered mothers

26. NATURE AND NURTURE INTERACTIONS Continuity of Behavior: Two Hypotheses The Hypotheses: Cumulative continuity –We make certain choices, deliberate or not deliberate, that determine what direction our life goes Interactional continuity –Early temperament forms an interactional style that evokes reciprocal, maintaining responses from others. The person acts, the environment reacts, and the person reacts back.

27. HOW DO NATURE AND NURTURE INTERACT? The Exotic Becomes Erotic (Bem, 1996) Biological Predisposition Childhood Temperaments Sex-Typical Activity And Playmate Preferences Feeling Different From Opposite Or Same-Sex Peers Nonspecific Autonomic Arousal To Opposite or Same-Sex Peers Erotic/Romantic Attraction (Sexual Orientation)

28. MAIN POINTS It does not really make sense to ask whether personality comes from nature or nurture, as it comes from a complex dynamic interaction of the two. Nature contributes to personality through genetics, as well as basic processes such as brain activation, inhibition to the unfamiliar, emotional reactivity, neuroanatomy, and biochemistry. Nurture contributes to personality through influences such as parental relationship, sibling competition, and peer group processes. Nature and nurture interact from infancy throughout the life span. Diathesis, cumulative continuity, and interactional continuity are some of the mechanisms through which these interactions occur.