CHAPTER 9. Biological Foundations of Personality. The Biological Tradition. Temperament

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1 CHAPTER 9 Biological Foundations of Personality The Biological Tradition Phineas Gage ( ) Temperament Individual differences in general mood or quality of emotional response that are moderately stable, inherited, and biologically based

2 Constitution of Temperament The 4 humors (Melancholic, Choleric, Sanguine, Phlegmatic) Phrenology Body Types Inhibited versus Uninhibited Children (Kagan, 1994) Inhibited n Reacts to unfamiliar people and situations with avoidance, distress, restraint n Takes longer time to relax in new situations n Has more fears and phobias n Is timid and cautious Uninhibited n Reacts to unfamiliar situations with spontaneity and joy n Takes shorter time to relax in new situations n Has fewer fears and phobias n Is not restrained in new situations Kagan, Arcus, & Snidman (1993) At 4-months, n Videotaped behavior during familiar and novel stimuli (voices, mobiles, balloons) n Rated infants on reactivity (body movement, crying) At 14-months, 21-months, 4.5 years, 8 years n Videotaped behavior and monitored physiology

3 High vs. Low Reactive Infants (Kagan et al., 1993) High reactive n Show greater fearful behavior, heart rate acceleration, increased blood pressure n Smiled and talked less with unfamiliar adult n Were shy with unfamiliar peer n Varied within group Low reactive n Showed lesser fearful behavior, heart rate acceleration, increased blood pressure n Smiled and talked more with unfamiliar adult n Were less shy with unfamiliar peer n Varied within group 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 Neurology and Freudian Defense Mechanisms

4 BRAIN PLASTICISTY The story of Jody: A case of hemispherectomy Behavioral Genetics Different ways of estimating genetic influence: Selective Breeding Twin studies Adoption studies Heritability Twin studies: Compare identical twins reared together with those reared apart Assume the similarity between Together twins due to shared genes and environment Assume the similarity between Apart twins due only to genes THEN: Similarity of together - Similarity of Apart = environment, and 1- environment = genes

5 Heritability Another form of twin study: Compare monozygotic (MZ) together twins with dyzygotic (DZ) together twins Assume similarity of MZ due to genes and environment Assume similarity of DZ due to 1/2 genes and environment Heritability THEN: Heritability = 2* (Similarity MZ - Similarity DZ) = 2*((genes + environment) - (1/2 genes + environment)) = 2* (genes +environment - 1/2 genes - environment) = 2*(genes - 1/2 genes) = 2*genes - genes = genes Heritability Heritability is an estimate of the percentage of the variance in a particular characteristic in a particular study that resulted from genetic variation in that study.

6 * * * * Variance * * * * * * * * * Friendliness Variance = ((1-5) 2 + (3-5) 2 + (3-5) (10-5) 2 ) / N-1 Average deviation 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 Heritability is: an estimate of the percentage of the variance in a particular characteristic in a particular study that resulted from genetic variation in that study.

7 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 H = 13% for male relatives and 30% for female relatives Vocational interests H =0.43 Religiosity H =0.49 Traditionalism H =0.53 Attitudes toward drinking alcohol H = 51% Radicalism and toughmindedness H > 50% Aggressive, antisocial, criminal behavior H about 50% 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. Epigenetics Example Oxytocin Receptor Polymorphism (rs53576) Gene and Culture Interaction (Kim et al., 2011)

8 NATURE AND NURTURE INTERACTIONS Diathesis-Stress Model Stress Level Patient Becomes Ill Critical Point Time Examples Schizophrenia (genetic diathesis) Phobias (environmental diathesis) Alcoholism (possible genetic/environmental) Depression (possible genetic/environmental) 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 NATURE AND NURTURE INTERACTIONS Continuity of Behavior: Two Hypotheses Cumulative continuity n We make certain choices, deliberate or not deliberate, that determine what direction our life goes Interactional continuity n Early temperament forms an interactional style that evokes reciprocal, maintaining responses from others. The person acts, the environment reacts, and the person reacts back.

9 MAIN POINTS ABOUT NATURE-NURTURE Personality comes from a complex dynamic interaction of nature and nurture Nature contributes to personality through genetics, as well as basic processes such as brain activation, temperment, neuroanatomy, and biochemistry. Nurture contributes to personality through influences such as parental relationship, sibling competition, environmental stimulation, and culture. Nature and nurture interact from the fetus throughout the life span. Diathesis, cumulative continuity, and interactional continuity are some of the mechanisms through which these interactions occur.