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Physiological approaches to personality
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Physiological Approaches to Personality

Sheldon's Physiological Approach to Personality
  • Argued that body type determines personality
    • Ectomorph (skinny): Thoughtful, introverted
    • Mesomorph (muscular): Assertive, bold
    • Endomorph (fat): Sociable, fun-loving
    • Did not use blind ratings, most later research failed to replicate
    • Some work suggesting relationship between body type and job choice
    • Physiological personality psychologists today do not focus on global variables such as body type—much more fine-tuned (e.g., heart rate, brain waves)
Physiological Measures Commonly Used in Personality Research
  • Electrodermal Activity (Skin Conductance)
    • Most obtained by electrodes or sensors placed on the skin surface
    • Advantage: Noninvasive, no discomfort
    • Disadvantage: Movement constrained
    • Electrodermal activity (EDA)—due to increased sweat with arousal, skin conductance of electricity increases
      • Can measure responses to various stimuli, including sudden noises, emotionally charged pictures, pain, anxiety, fear, guilt
      • Some people show EDA in the absence of external stimuliÑassociated with anxiety and neuroticism
  • Cardiovascular activity
    • Blood pressure—measure of, e.g., stress reactivity
    • Heart rate—increases with anxiety, fear, arousal, cognitive effort
    • Cardiac reactivity—greater than normal increase in blood pressure and heart rate when performing task such as backward serial subtraction
      • Associated with Type A personality—impatience, competitiveness, hostility
      • Cardiac reactivity (and Type A) associated with coronary heart disease
    Brain Electrical Activity
    • Brain spontaneously produces small amounts of electrical activity; can be measured by electrodes on scalp—electroencephalograph (EEG)
    • Evoked potential technique—uses EEG, but the participant is given a stimulus and the researcher assess specific brain response to stimulus
    • Brain imaging techniques—map structure and function of brain
      • Positron emission tomography (PET)
      • Functional magnetic resonance imaging (fMRI)
    Other measures: Biochemical analyses of blood and saliva
Physiologically Based Dimensions of Personality
    • Measured by Eysenck Personality Questionnaire (EPQ)
    • High extraversion: Talkative, outgoing, likes meeting new people and going to new places, active, sometimes impulsive, bored easily, hates routine
    • Low extraversion: Quiet, withdrawn, prefers being alone or with a few friends to large crowds, prefers routines and schedules, prefers familiar to unexpected
    • Eysenck's theory
      • Introverts have a higher level than extraverts of activity in the brain's ascending reticular activating system (ARAS)
      • People strive to keep ARAS activity at optimal level—introverts work to decrease it and avoid stimulation; extraverts work to increase it and seek out stimulation
      • Research indicates that introverts and extraverts are NOT at different resting levels, but introverts ARE more reactive to moderate levels of stimulation than extraverts
      • This work led Eysenck to revise his theory—the difference between introverts and extraverts lies in arousability, not in baseline arousal
      • When given a choice, extraverts prefer higher levels of stimulation than introverts
      • Geen (1984): Introverts and extraverts choose different levels of stimulation, but equivalent in arousal under chosen stimulation
      • Introverts and extraverts perform task best under their chosen stimulation level, poor when performing under a stimulation level chosen by other group
    Sensitivity to Reward and Punishment
    • Personality based on two hypothesized brain systems
    • Behavioral Activation System (BAS): Responsive to incentives (cues to reward) and regulates approach behavior
    • Behavioral Inhibition System (BIS): Responsive to cues to punishment, frustration, uncertainty, and motivates ceasing, inhibiting, or avoidance behavior
    • Active BIS produces anxiety, active BAS produces impulsivity
    • Integration with Eysenck's model: Impulsive = high extraversion, moderate neuroticism; Anxious = moderate introversion, high neuroticism
    • According to Gray, impulsive people do not learn well from punishment because of weak BIS; learn better from rewardÑsupported by research
    Sensation Seeking
    • Tendency to seek out thrilling, exciting activities, take risks, avoid boredom
    • Early sensory deprivation research
    • Hebb's theory of optimal level of arousal
    • Zuckerman: High sensation seekers are less tolerant of sensory deprivation; require much stimulation to get to optimal level of arousal
    • Zuckerman's Sensation Seeking Scale
    • Moderate positive correlation between extraversion and sensation seeking
    • Physiological basis for sensation seeking
      • Neurotransmitters—chemicals in nerve cells are responsible for the transmission of nerve impulse from one cell to another
      • Monoamine Oxidase (MAO)—enzyme that maintains a proper level of neurotransmitters
      • Too little MAO = too much neurotransmitter; too much MAO = too little neurotransmitter
      • High sensation seekers have low levels of MAO, producing a need for stimulation to reach the optimal level of arousal
    Neurotransmitters and Personality
    • Dopamine—associated with pleasure
    • Serotonin—associated with depression and other mood disorders
    • Norepinepherine—associated with fight or flight response
    • Cloninger's Tridimensional Personality model
      • Novelty seeking—low levels of dopamine
      • Harm avoidance—low levels of serotonin
      • Reward dependence—low levels of norephinepherine
    Strength of the Nervous System
    • Pavlov's personality theory—based on work with dogs
      • Some dogs have "strong nervous system"—can tolerate and need strong stimulation
      • Other dogs have "weak nervous system"—cannot tolerate and do not seek out stimulation
      • Pavlov studied individual differences in conditionability in dogs
        • Dogs with weak nervous systems conditioned more quickly than dogs with strong nervous systems
    • Later application to humans
      • People with weak nervous systems are more sensitive to stimulation but unable to endure strong stimulation for a long period
      • People with strong nervous systems are insensitive to weak stimulation but able to endure strong stimulation for long periods
      • Strelau sought to translate the concept of the strength of the nervous system from the level of the nerve cell (Pavlov) to the level of human behavior
        • Strelau demonstrated common elements among traits of reactivity, sensation seeking, extraversion (strong nervous system)
        • Common biological reactivity dimension may account for overlapping dimension
    • Being a "morning-type" or "evening-type" of person is a stable characteristic
    • Due to differences in underlying biological rhythms
    • Many biological processes fluctuate around a 24-25 hour cycle#8212;circadian rhythm; e.g., body temperature, endocrine secretion rates
    • But wide individual differences are in the circadian rhythm, identified through temporal isolation studies
      • Individuals with shorter circadian rhythms hit peak body temperature and alertness earlier in day, get sleepy earlier, than individuals with longer rhythm
      • Individuals with shorter rhythm tend to be morning persons; individuals with longer rhythms tend to be evening persons
      • Morningness-Eveningness Questionnaire
      • Cross-cultural replication and documentation of stability of characteristic
    Brain Asymmetry and Affective Style
    • Left and right sides of the brain are specialized, with asymmetry in control of psychological functions
    • Using EEG, can measure brain waves, such as alpha wave#8212;an inverse indicator of brain activity
    • Left frontal hemisphere is more active than the right when a person is experiencing pleasant emotions; right is more active than left with unpleasant emotions
    • Patterns replicated in adults, children, and infants
    • Research indicates that the tendency to exhibit asymmetry (favoring left over right, or right over left activation) is a stable individual characteristic
    • Dispositionally positive persons show greater left frontal EEG activity; dispositionally negative persons show greater right frontal EEG activity
Conclusion: Person's affective lifestyle may have origins in, or be predicted by a pattern of asymmetry in frontal brain activation