Biology & Personality

Phineas Gage video Early evidence of brain & temperament Brain injury changed disposition Role of body & brain in consistencies of behavior? Extraverted bodies? Emotionally (un)stable brains?

Outline Temperament Evolution and personality Behavioral genetics Brain and temperament

Temperament Individual differences in affective response Inherited Biologically based Evidence from birth & stable throughout life NOT traits but related Traits not stable from birth & less pervasive influence

Temperament Early views linked T w/ body features Gall & phrenology Kretschmer, Sheldon & body types Inherited body determines T Direction of effect problem Recent work finds that endo NOT jolly

Temperament: Recent Research New York Longitudinal Study (Thomas & Chess, 1977) Kids followed from birth (1950) - adolescence Parental reports revealed easy, difficult, & slow-to-warm-up babies Associated w/ later adjustment

Temperament: Recent Research Kagan (1999): Inhibited v. uninhibited kids Laboratory observations of 4 month olds revealed high & low reactivity Stability of T at 4/8 years old Change also due to parental influence

Temperament: Recent Research In sum temperament construct supported Link between biology & personality Reciprocally causal Temperaments linked w/ Big-5 (guide trait development) Emotionality (~N) Activity (~E) Sociability (~E)

Jealousy On a clean sheet of paper answer this Q: What would bother you more: Your boy/girl friend (spouse) having sex with someone else or developing emotional feelings for someone else? Sexual or emotional infidelity? What is your gender?

Evolutionary Theory Characteristics associated w/ survival selected Ultimate causes of current behavior tendencies Evolved psychological mechanisms (specific) Nature of human nature (e.g., social) Individual differences Directional v. stabilizing selection Niches

Activity 9: Gender Differences Provide a critical analysis of the research examining evolutionary predictions regarding gender differences in mate preferences & jealousy. Does the evidence support these claims? Can you think of any alternative explanations? PLEASE TURN THIS IN AFTER CLASS!

Gender Differences Problems w/ evidence for evolutionary account 1. Failures to replicate Some studies find most men choose emotional infidelity No gender differences in physiology 2. All forced choice methodology No gender difference w other methods

Gender Differences Harris (2002) Forced choice M > W on sexual

Gender Differences Harris (2002) Recalled episode of infidelity No gender effects Both more bothered by emotional

Gender Differences 3. Cultural/social theories: Similar predictions Social Exchange Theory Men control resources, women control sex Women give sex to men in exchange for resources Women most upset about losing resources (love = shifting loyalties) & choose resource-rich mate Men most upset about losing sex & choose sexy mate

Day 2

Behavioral Genetics Examine contribution of nature & nurture Twin & adoption studies Heritability coefficient (h2) Findings: h2s ~ .40 Specific to population Not fate Not single genes “Bummer of a Birthmark Hal”

Shared & Non-Shared Environment Variability in characteristics in population 40% genetic 40% environment (+ 20% error) Shared (same family, house, etc.): 5% Non-shared (unique experiences, including perceived even w/in same family): 35%

Shared & Non-Shared Environment Similar environments have little impact Similar experiences do not -> personalities more alike Genes make us similar Non-shared environment makes us different

Reaction Paper 7: Rearing Influences How much variability in personality is due to shared environmental influences? Does this suggest that rearing practices & parents are not important in personality development? Was Dan Quail wrong in saying single parent homes are bad for the children?

Neuroscience & Personality Where in the brain is personality? Specific areas & systems show individual differences

Amygdala Motivation & emotion Damage impairs NA Rs Arousability linked w/ T Metabolically linked w/ N

Amygdala Neurotics have rapid amygdalar metabolism Impair NA repair, decay Explain NA of neurotics? Irwin et al (2000)

Ascending Reticular Activation Formation (ARAS) Located w/in brain stem & controls arousal Individual differences in reactivity Extraversion due to reactivity of ARAS Baseline higher among I Response to stimulation stronger among I

Extraversion and ARAS arousal

Optimal Arousal Comfortable functioning Es under-aroused & should prefer high stimulation activities Is over-aroused & should prefer low stimulation activities Stimulus shy (I) or Stimulus hungry (E)

Evidence Task choice Physiological arousal Task performance E choose higher stimulating behavior than I Physiological arousal I > E for given level of stimulation Task performance Is do better at monotonous jobs (air traffic) & moderate levels of stimulation Es do better at fast paced jobs & higher levels of stimulation

Approach & Inhibition Systems 2 Brain system involved with: Approach behaviors & positive emotions Inhibit behaviors & negative emotions Key are individual differences in the reactivity of these brain systems

Behavioral Approach System (BAS) Structures in left Pre Frontal Cortex (PFC) Cause approach behavior (GO!) during incentives Controls positive emotions Individual differences in reactivity (hi lo) Associated w/ E & uninhibited T

Behavioral Inhibition System (BIS) Structures in right Pre Frontal Cortex (PFC) Cause avoidance/inhibitory behavior (Stop/Reverse!) Activated during punishment/danger/threat Controls negative emotions regarding punishment Individual differences in reactivity (hi lo) Associated w/ N & inhibited T

BAS/BIS Measurement EEG activity Self-Report Measures High baseline (left or right PFC) & strong response to positive or negative stimuli Self-Report Measures Reward or Punishment sensitivities, seek/avoid When I get something I want I feel excited & energized Criticism or scolding hurts me quite a bit Correlated w/ PFC activity

BAS & BIS Independent dimensions Individual differences on both All combinations possible These combos are key for understanding personality BIS

Neurotransmitters BAS, PE associated w/ dopamine Genes producing dopamine & dopamine reactivity linked to self-reported BAS BIS, NE associated w/ serotonin Genetic evidence mixed