Physiological approaches to personality |  |
Chapter OutlinePhysiological 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
Extraversion-Introversion
- 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- Low extraversion: Quiet, withdrawn, prefers being alone or with a few friends to large crowds, prefers routines and schedules, prefers familiar to unexpected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
Morningness-Eveningness
- 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
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2002 McGraw-Hill Higher Education