BIOLOGICAL FACTOR THEORIES

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EYESENK’S PEN MODEL

People whose excitatory processes are stronger (who have a “strong nervous system”) are extraverts, whereas those with relatively greater inhibitory processes (who have a “weak nervous system”) are introverts.

Extraversion is the first of Eysenck’s three proposed factors of personality. The others, also based on biological differences between people that are inherited are Neuroticism and Psychoticism. (Rearranging the first letters of these factors gives the acronym “PEN.”)

The second factor in Eysenck’s model is Neuroticism. Greater activity in the limbic system causes some people to become more emotionally aroused when they are threatened or placed in stressful situations. These people are high in the factor of Neuroticism. Others, low on that factor, do not become so emotional in the same situation. Greater emotional arousal can, in turn, cause neurotics to make use of defense mechanisms; hence the term neuroticism.

Eysenck’s third factor refers to a tendency toward nonconformity or social deviance (Zuckerman, Kuhlman, & Camac, 1988). Eysenck (1992) labeled this factor Psychoticism.

GRAY’S REINFORCEMENT SENSITIVITY THEORY

J. A. Gray (1987) proposes a biological theory of personality that builds on Eysenck’s theory. Gray proposes that individuals vary in motivational systems related to positive and negative reinforcement (approach and avoidance). Some people emphasize approach and positive emotions, whereas others emphasize avoidance and negative emotions.

Behavioral Activation System (BAS) in Gray’s model, is the tendency of personality related to the approaching of rewarding experiences.

Behavioral Inhibition System (BIS) in Gray’s model, is the tendency of personality related to reactions to aversive stimuli.
Fight-flight System (FFS) is the biological personality factor proposed by Gray that produces rage and panic.

According to Gray’s theory, extraverts are more influenced by reward, introverts by punishment. As predicted by this theory, in an experimental task in which auditory signals sometimes signaled reward and sometimes punishment, introverts showed more brain wave reaction to signals of punishment for an incorrect response, and extraverts showed more brain wave reaction to signals of reward for a correct response.

Activation of the BAS and BIS does not simply produce pleasant and unpleasant emotion, but it also guides learning. Rewards and punishments are cues that teach us what to approach and what to avoid. Combining biological mechanisms with the impact of learning, as Gray’s theory does, offers considerable promise for understanding personality as it is inherited and as it changes with experience.

CLONINGER’S TRIDIMENSIONAL MODEL

C. R. Cloninger’s tridimensional model proposes three biologically based personality traits, each resulting from the relative level of a particular neurotransmitter in a person’s central nervous system. These three dimensions can be considered temperament types, the biological foundation on which personality, through experience, is developed.

The first temperament trait, novelty seeking, is related to levels of the neurotransmitter dopamine (with low levels of dopamine producing greater novelty seeking). It serves as a behavioral activation system. People high in novelty seeking become more excited in response to novel stimuli, and they explore their environments more. They seek excitement and try new things for the thrill of it. Novelty seeking is higher among those who abuse drugs, although sometimes substance abuse is produced by the second genetic trait, harm avoidance (Berman et al., 2002).

The second temperament trait, harm avoidance, is related to high levels of the neurotransmitter serotonin. It serves as a behavioral inhibition system. People high in this trait are highly influenced by aversive stimuli or by signals indicating they will be punished, and so they act to avoid pain. They report that they worry and feel tense. Conversely, low serotonin activity is associated with impulsive acts of aggression, including murder, suicide, and arson (Coccaro et al., 1989).

The third temperament trait, reward dependence, results from low levels of the neurotransmitter norepinephrine. It serves as a behavioral maintenance system, making people continue to behave in ways that produce reward, especially reward through warm social attachments (Stallings et al., 1996). People who are high in reward dependence report that they are hardworking and keep working even if others have given up.

These temperament dimensions are scored from a self-report measure, the Tridimensional Personality Questionnaire (TPQ). Here are some examples of items (listed by Stallings et al., 1996):

I do things spontaneously. (Novelty Seeking)
I get tense and worried in unfamiliar situations. (Harm Avoidance)
Others think I am too independent. (disagree; Reward Dependence)
I often push myself to exhaustion. (Persistence component of Reward Dependence)

IN A NUTSHELL

Biological understandings of personality have been offered from the evolutionary shared traits of our species to individual differences in genetic inheritrance and brain functioning.

• At the level of evolution, natural selection based on reproductive success offers explanations for sexual selectivity and jealousy, aggression, altruism, and nurturance; many of these traits vary between males and females.
• The immaturity of human young, combined with human capacity for language and imitation, prepare for considerable influence of experience.
• Cultural evolution supplements biological changes.
• Heredity has widespread influences on individual differences in personality.
• Temperament differences are observable early in life, and they are the basis for adult personality differences.
• Studies of the brain and nervous system find specific areas for many human traits. Emotion and arousal are particularly important.
• Several biological factor theories have been proposed (including those by Eysenck, Gray, and Cloninger).
• Eysenck’s PEN model describes Extraversion, Neuroticism, and Psychoticism.
• Gray’s reinforcement sensitivity theory proposes a Behavioral Activation System (BAS) that emphasizes rewards and a Behavioral Inhibition System (BIS) that emphasizes punishments.
• Cloninger’s tridimensional model describes three factors: Novelty Seeking, Harm Avoidance, and Reward Dependence.
• All of these biological aspects of personality are subject to influences from experience and culture.

Reference - Theories of Personality - Understanding Persons, Susan Cloninger, The Sage Colleges, 6th edition

This article is part of Personality Course series. If you miss previous articles, you can find them below.

Personality Course	Sigmund Freud
Carl Jung	Alfred Adler
Erik Erikson	Karen Horney
Gordon Allport	Raymond Catell

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