Trait theory

In psychology, Trait theory is a major approach to the study of human personality. Trait theorists are primarily interested in the measurement of "traits", which can be defined as habitual patterns of behavior, thought, and emotion. [Saul Kassin, (2003). "Psychology". USA: Prentice-Hall, Inc.] According to this perspective, traits are relatively stable over time, differ among individuals (e.g. some people are outgoing whereas others are shy), and influence behavior.

Gordon Allport was an early pioneer in the study of traits, which he sometimes referred to as dispositions. In his approach, "central traits" are basic to an individual's personality, whereas "secondary traits" are more peripheral. "Common traits" are those recognized within a culture and may vary between cultures. "Cardinal traits" are those by which an individual may be strongly recognized. Since Allport's time, trait theorists have focused more on group statistics than on single individuals. Allport called these two emphases "nomothetic" and "idiographic," respectively.

There is a nearly unlimited number of potential traits that could be used to describe personality. The statistical technique of factor analysis, however, has demonstrated that particular clusters of traits reliably correlate together. Hans Eysenck has suggested that personality is reducible to three major traits. [Hans Eysenck, (1967). "The biological basis of personality." Springfield, IL: Thomas.] [Hans Eysenck, (1991). Dimensions of personality: 16: 5 or 3? Criteria for a taxonomic paradigm. "Personality and Individual Differences", "12", 773-90.] Other researchers argue that more factors are needed to adequately describe human personality. [Saucier, G., & Goldberg, L. R. (1998). What is beyond the Big Five? "Journal of Personality", "66", 495–524.] Many psychologists currently believe that five factors are sufficient. [McCrae, R. R., & Costa, P. C., Jr. (1987). Validation of the five-factor model across instruments and observers. "Journal of Personality and Social Psychology", "52", 81–90.] [Costa, P. T., & McCrae, R. R. (1992). Four ways five factors are basic. "Personality and Individual Differences", "13", 653-665.]

Virtually all trait models, and even ancient Greek philosophy, include extraversion vs. introversion as a central dimension of human personality. Another prominent trait that is found in nearly all models is Neuroticism, or emotional instability.

Two taxonomies

Eysenck's three factor model contains the traits of extraversion, neuroticism, and psychoticism. The five factor model contains openness, extraversion, neuroticism, agreeableness, and conscientiousness. These traits are the highest-level factors of a hierarchical taxonomy based on the statistical technique of factor analysis. This method produces factors that are continuous, bipolar, can be distinguished from temporary states, and can describe individual differences. [Goldberg, L. R. (1993). The structure of phenotypic personality traits. "American Psychologist", "48", 26–34.] Both approaches extensively use self-report questionnaires. The factors are intended to be orthogonal (uncorrelated), [Hans Eysenck, (1990). Biological dimensions of personality. In L. A. Pervin (Ed.), "Handbook of personality: Theory and research" (pp. 244-276). New York: Guilford.] though there are often small positive correlations between factors. The five factor model in particular has been criticized for losing the orthogonal structure between factors. [Block, J. (1995). A contrarian view of the five-factor approach to personality description. "Psychological Bulletin", "117", 187–215.] [Draycott, S. G., & Kline, P. (1995). The Big Three or the Big Five - the EPQ-R vs the NEO-PI: a research note, replication and elaboration. "Personality and Individual Differences", "18", 801-804.] Hans Eysenck has argued that fewer factors are superior to a larger number of partly related ones. [Eysenck, H. J. (1992). A reply to Costa and McCrae. P or A and C: The role of theory. "Personality and Individual Differences", "13", 867-868.] Although these two approaches are comparable because of the use of factor analysis to construct hierarchical taxonomies, they differ in the organization and number of factors.

Whatever the causes, however, psychoticism marks the two approaches apart as the five factor model contains no such trait. Moreover, apart from simply being a different high-level factor psychoticism, unlike any of the other factors in either approach, does not fit a normal distribution curve. Indeed, scores are rarely high thus skewing a normal distribution. [Matthews, G., Deary, I.J., & Whiteman, M.C. (2003). "Personality traits" (2nd edition). Cambridge: Cambridge University Press.] However, when they are high there is considerable overlap with psychiatric conditions such as antisocial and schizoid personality disorders. Similarly, high scorers on neuroticism are more susceptible to sleep and psychosomatic disorders. [Hans Eysenck and S. B. G. Eysenck. (1991). The Eysenck Personality Questionnaire-Revised. Sevenoaks: Hodder & Stoughton.] Five factor approaches can also predict future mental disorders, [Costa, P. T., & McCrae, R. R. (1990). Personality disorders and the five factor model of personality. "Journal of Personality Disorders", "4", 362-371.] [Lynam, D. R., Caspi, A., Moffitt, T. E., Raine, A., Loeber, R., & Stouthamer-Loeber, M. (2005). Adolescent psychopathy and the Big Five: Results from two samples. "Journal of Abnormal Child Psychology", "33", 431-443.]

Lower order factors

There are two higher order factors that both taxonomies clearly share, extraversion and neuroticism. Both approaches broadly accept that extraversion is associated with sociability and positive affect, whereas neuroticism is associated with emotional instability and negative affect. [Matthews, G., Deary, I.J., & Whiteman, M.C. (2003). "Personality traits" (2nd edition). Cambridge: Cambridge University Press.] Many lower order factors are similar between the two taxonomies. For instance, both approaches contain factors for sociability/gregariousness, for activity levels, and for assertiveness within the higher order factor, extraversion. However, there are differences too. First, the three-factor approach contains nine lower order factors and the five-factor approach has six. [Matthews, G., Deary, I.J., & Whiteman, M.C. (2003). "Personality traits" (2nd edition). Cambridge: Cambridge University Press.] Eysenck's psychoticism factor incorporates some of the polar opposites of the lower order factors of openness, agreeableness and conscientiousness. A high scorer on tough-mindedness in psychoticism would score low on tender-mindedness in agreeableness. Most of the differences between the taxonomies stem from the three factor model's emphasis on fewer high-order factors.

Causality

Although both major trait models are descriptive, only the three factor model offers a detailed causal explanation. Eysenck suggests that different personality traits are caused by the properties of the brain, which themselves are the result of genetic factors. [Eysenck, H. J., & Eysenck, M. W. (1985). "Personality and individual differences: A natural science approach." New York: Plenum.] In particular, the three factor model identifies the reticular system and the limbic system in the brain as key components, with the specific functions of mediating cortical arousal and emotional responses respectively. Eysenck advocates that extraverts have low levels of cortical arousal and introverts have high levels, leading extraverts to seek out more stimulation from socialising and being venturesome.. [Eysenck, H.J. (1967). "The biological basis of personality." Springfield, IL: Thomas.] Moreover, Eysenck surmised that there would be an optimal level of arousal after which inhibition would occur and that this would be different for each person. [Eysenck, H. J. (1994). Creativity and personality: Word association, origence, and Psychoticism. "Creativity Research Journal", "7", 209-216.] In a similar vein, the three factor approach theorizes that neuroticism is mediated by levels of arousal in the limbic system with individual differences arising because of variable activation thresholds between people. Therefore, highly neurotic people when presented with minor stressors, will exceed this threshold, whereas people low in neuroticism will not exceed normal activation levels, even when presented with large stressors. By contrast, proponents of the five factor approach assume a role of genetics and environment but offer no explicit causal explanation.

Given this emphasis on biology in the three factor approach it would be expected that the third trait, psychoticism, would have a similar explanation. However, the causal properties of this state are not well defined. Eysenck has suggested that psychoticism is related to testosterone levels and is an inverse function of the serotonergic system, [Eysenck, H. J. (1992). The definition and measurement of psychoticism. "Personality and Individual Differences", "13", 757-785.] but he later revised this, linking it instead to the dopaminergic system. [Eysenck, H. J. (1997). Personality and experimental psychology: The unification of psychology and the possibility of a paradigm. "Journal of Personality and Social Psychology", "73", 1224-1237.]

ee also

*16 Personality Factors
*Big five personality traits
*Hans Eysenck
*NEO-PI
*Personality psychology

References