Personality theory has been dominated by two different forces. On one side, psychoanalysts and humanistic psychologists; and on the other, trait theorists. Trait theorists have largely devoted themselves to administering tests to uncover personality traits. J. P. Guilford, a prominent personality test designer, produced the 1959 de?nition of trait that remains the standard: a trait is “any relatively enduring way in which one individual differs from another.”
This has left room for many different personality theories based on traits. An early trait theorist, Gordon Allport, attempted to make a list of all trait terms in the English language and came up with many thousands. One reason for this has to do with our tendency to have several labels for a single trait (shy, timid, and introverted, for example). According to Allport, when trait terms are distilled down to a set of nonoverlapping adjectives that describe reasonably distinct traits, the remaining set still consists of several hundred. For this reason, trait theorists have come up with very different sets of traits when attempting to describe human personality.
Raymond Cattell, for example, has identi?ed sixteen source traits, which are the basis for his popular 16PF (Sixteen Personality Factors) personality inventory.
Another trait theorist, Eysenck, on the other hand, produced a similarly popular personality test (the Eysenck Personality Questionnaire, or EPQ) based on “Big Five” Personality Factors the notion that personality consists of just two basic dimensions: introversion extraversion and emotional stability-instability.
The Comrey Personality Scales measure eight dimensions of personality.
Several different personality tests (including the Edwards Personal Preference Schedule and the Personality Research Form) are based on Henry Murray’s description of personality as being determined by a set of twenty basic needs.
To sort out this confusion, personality psychologist L. R. Goldberg proposed the fundamental lexical hypothesis: that the most important individual differences between humans will come to be single terms in the world’s languages. This means that any term that has endured for describing differences between people could theoretically represent a trait that someone might be able to measure. This would unfortunately result in potentially thousands of possible traits, but in 1981 Goldberg came up with a solution that has caught on with surprising speed among personality theorists and researchers. In his examination and analysis of the entire research literature on personality traits, he identi?ed ?ve traits that frequently and consistently appeared in most attempts to de?ne the basic human factors. Although researchers have used many different words for them, the ?ve most commonly identi?ed personality factors are: neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness. Those factors are now known as the Big Five. These labels, each a continuum, rather than a characteristic a person either does or does not have, represent the following:
Neuroticism—Now frequently referred to as emotional stability or instability. At one extreme of the continuum, a person would be calm, secure, and self-satis?ed, whereas at the other extreme are those who are anxious, insecure, and self-pitying.
Extraversion—This trait originated with Carl Jung and was also central to Eysenck’s model. Jung chose the words introversion and extraversion because they mean, respectively, inner-directed and outer-directed. At one end of the continuum are people who are sober, reserved, and withdrawn, while those at the other end are sociable, fun-loving, and affectionate.
Openness to Experience—At one end of the continuum are people who are independent and imaginative, with a preference for variety, while those at the other extreme are practical conformists who prefer a set routine.
Agreeableness—This continuum has people who are excessively trusting, helpful, and soft-hearted, arrayed against the ruthless, suspicious, and uncooperative people on the other side.
Conscientiousness—The highly conscientious person is organized, careful, disciplined, and reliable, whereas the other end of the continuum includes people who are disorganized, careless, and impulsive.
These traits all represent a broad spectrum of personality and behavior. Few people are at either extreme; most are located somewhere in the vast middle ground between the extremes. A team of psychologists and historians once attempted to retrospectively assign all U.S. presidents to scores on the Big Five. Not surprisingly, Richard Nixon scored high in neuroticism and fairly low on the other traits, whereas Bill Clinton scored very high in extraversion and openness to experience.
A well validated personality test based on the Big Five, the Neo-Personality Inventory-Revised (NEO-PI-R), has come into very wide use, allowing extensive research to be done on the Big Five, and so quite a bit is already known about these personality dimensions. For one thing, scores on the Big Five appear to be quite stable over time, with three of them tending to wane somewhat in adulthood (neuroticism, extraversion, and openness), while the other two (conscientiousness and agreeableness) increase during the same period. It also appears that about 50 percent of the variability in the ?ve dimensions may be inherited. A frequent criticism of personality theories is that they can be somewhat culture-speci?c, but the Big Five appear to describe personality pretty well in a variety of cultures. The real test for a personality theory, however, is whether it can predict any other areas of psychological functioning. Here again, the Big Five show promise. In a study of people with different circadian rhythm patterns, highly conscientious people were more likely to be “morning people,” while “night people” were found to be more extraverted. Much research remains to be done, but the Big Five has brought back to life the study of trait conceptions of personality.