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-towarm-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
Introvert
8
7
6
5
4
3
2
Base line
Stim ulation
Extravert
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
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
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
BAS
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