Biological Substrates of Personality

Central nervous system structure and function

Frontotemporal lobar degeneration Personality change (more apathetic, less social, more emotionally blunted)

Eysenck Returns: Extraversion

Ascending reticular activation system: regulates arousal, wakefulness

Baseline arousal + environmental arousal = total arousal

Central nervous system structure and function

Eysenck Returns: Extraversion

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Introvert Extravert

Brain Environment

Ascending reticular activation system: regulates arousal, wakefulness

Baseline arousal + environmental arousal = total arousal

Biological Substrates of Personality

Autonomic nervous system

Sympathetic and parasympathetic branches

Eysenck Returns: Extraversion

Ascending reticular activation system: regulates arousal, wakefulness

Baseline arousal + environmental arousal = total arousal

Baseline arousal determines environmental choices to regulate total arousal

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Introvert noise choice Extravert noise choice

Introverts Extraverts

(From Geen, 1984)

Central nervous system structure and function

Limbic system (hippocampus, amygdala, septum, prefrontal cortex, and others) is the seat of the emotions

Eysenck Returns: Neuroticism

BIS and BAS

Behavioral approach system (BAS) is thought to be mediated by the basal ganglia, which can disinhibit other structures

Reward-seeking

Behavioral inhibition system (BIS) is thought to be mediated by the frontal cortex and limbic system

Punishment-avoiding

Central nervous system structure and function

BIS and BAS

Behavioral approach system (BAS) is also associated with greater left than right hemispheric activation in the frontal lobes

Reward-seeking

Behavioral inhibition system (BIS) is, conversely, associated with greater right than left hemispheric activation

Punishment-avoiding

Central nervous system structure and function

Biological Substrates of Personality

Transmitter systems

Major brain transmitters: serotonin (5HT), norepinephrine (NE), dopamine (DO). Systems are affected by production, reception, and potentiation.

Transmitter systems

Can drugs that affect neurotransmitters affect personality?

Selective serotonin reuptake inhibitors

Examples: Prozac (fluoxetine, 1988); Serzone (1990), Celexa (1991), Paxil (1992), Zoloft (1993), Luvox (1994), Remeron (2001), and so on

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Number of US prescriptions per year

Transmitter systems

Listening to Prozac (Kramer, 1997)

“I believe Tess’s story contains an unchronicled reason for Prozac’s enormous popularity: its ability to alter personality. Here was a patient whose usual method of functioning changed dramatically. She became socially capable, no longer a wallflower but a social butterfly. Where once she had focused on obligations to others, now she was vivacious and fun-loving. Before, she had pined after men; now she dated them, enjoyed them, weighed their faults and virtues. Newly confident, Tess had no need to romanticize or indulge men’s shortcomings.”

Tess: eldest of 10 children from impoverished, abusive background; history of maternal depression; married at 17 to abusive, alcoholic husband and later divorced; multiple symptoms of major depressive disorder; treated with Prozac for 2 weeks

Transmitter systems

Listening to Prozac (Kramer, 1997)

Tess: eldest of 10 children from impoverished, abusive background; history of maternal depression; married at 17 to abusive, alcoholic husband and later divorced; multiple symptoms of major depressive disorder; treated with Prozac for 2 weeks

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Depression improvement

Natural history

Placebo

Prozac

Transmitter systems

“Selective Alteration of Personality and Social Behavior by Serotonergic Intervention” (Knutson et al., 1998, American Journal of Psychiatry)

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Affiliation Negative affect Positive affect Hostility

SSRI Placebo

Affiliation: suggestions vs. commands, grasps in a cooperative puzzle task

Temperament

Defining characteristics in common with a general definition of personality:

individual differencestable

Defining characteristics specific to temperament:

partially heritableneurophysiological underpinningspresent during early life

Temperament

Inhibited temperament (Jerome Kagan)

Defining characteristics in common with a general definition of personality:

individual difference: inhibited children (15-20%) are shy, timid, fearful, restrained; uninhibited children (20-25%) are bold, spontaneous, fearlessstable: infant tests predict play styles in childhood

Defining characteristics specific to temperament:

partially heritable: boys MZ r = .64, DZ r = .25girls MZ r = .45, DZ r = .22

neurophysiological underpinnings: SNS arousabilitypresent during early life: evident as early as 4 months of age

Temperament

Other kinds of temperament (Buss and Plomin, others)

activity: energy, physical movement, squirming

positive emotionality/sociability: enjoy interactions with others

negative emotionality: easily upset, fussing, crying

impulsivity/distractability: less careful and thoughtful, easily distractable

approach-withdrawal: similar to BIS/BAS

Sex differences: Personality of 313

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O C E A N

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Women:

AgreeableEmpatheticTrustingExtravertedAnxious

Men:AggressiveAssertive

No difference:ImpulsiveOrderlyOpenReflective

Sex differences: Hormonal systems

testesovariesadrenal gland

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5ARD (5-alpha-reductase deficiency)

Converts T to DHT – DTH is necessary for development of male external genitalia. Virilisation may occur at puberty.

“Huevo a los doces” (Dominican Republic)

Autosomal recessive inheritance

Sex differences: Hormonal systems

Children: congenital adrenal hyperplasia and prenatal exposure to androgens

Men: correlations between T and crime, education, profession, and marriage

Women: study of 87 maximum-security inmates (aged 17-60)

T 1 2 3

1. age -.43

2. criminal violence .18 .05(theft vs. self-defense vs. homicide, assault)

3. aggressive dominance .34 -.25 -.25(trouble, aggression, domination, violations)

Sex differences: Evolution and mating strategies

Issue Females Males

Reproductive constraints A limited number of children No constraints on reproduction

Optimal strategy Best quality mate Largest number of mates

Desired mate quality Resources, fidelity Childbearing capacity, promiscuity

Indications of quality Earning capacity, status, Physical attractiveness, health,possessions, generosity, youthambition

Most likely basis for jealousy Sexual infidelity with other Emotional attachment to otherby partner (certainty of paternity) (certainty of resources)

Sex differences: Evolution and mating strategies

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Would you goout with me

tonight?

Would youcome over tomy apartment

tonight?

Would you goto bed with

me?

Men Women