Trait theories

According to the Diagnostic and Statistical Manual of the American Psychiatric Association, personality traits are "enduring patterns of perceiving, relating to, and thinking about the environment and oneself that are exhibited in a wide range of social and personal contexts." Theorists generally assume a) traits are relatively stable over time, b) traits differ among individuals (e.g. some people are outgoing while others are reserved), and c) traits influence behavior.

The most common models of traits incorporate three to five broad dimensions or factors. The least controversial dimension, observed as far back as the ancient Greeks, is simply extraversion and introversion (outgoing and physical-stimulation-oriented vs. quiet and physical-stimulation-averse).

• Gordon Allport delineated different kinds of traits, which he also called dispositions. Central traits are basic to an individual's personality, while secondary traits are more peripheral. Common traits are those recognized within a culture and thus may vary from culture to culture. Cardinal traits are those by which an individual may be strongly recognized.
  
• Raymond Cattell’s research propagated a two-tiered personality structure with sixteen "primary factors" (16 Personality Factors) and five "secondary factors."
  
• Hans Eyesnck believed just three traits—extraversion, neuroticism and psychoticism—were sufficient to describe human personality. Differences between Cattell and Eysenck emerged due to preferences for different forms of factor analysis, with Cattell using oblique, Eysenck orthogonal, rotation to analyse the factors that emerged when personality questionnaires were subjected to statistical analysis. Today, the Big Five factors have the weight of a considerable amount of empirical research behind them, building on the work of Cattell and others.
  
• Lewis Goldberg proposed a five-dimension personality model, nicknamed the “Big Five”.
  1. Openness to Experience: the tendency to be imaginative, independent, and interested in variety vs. practical, conforming, and interested in routine.
  2. Conscientiousness: the tendency to be organized, careful, and disciplined vs. disorganized, careless, and impulsive.
  3. Extraversion: the tendency to be sociable, fun-loving, and affectionate vs. retiring,somber, and reserved.
  4. Agreeableness: the tendency to be softhearted, trusting, and helpful vs. ruthless,suspicious, and uncooperative.
  5. Neuroticism: the tendency to be calm, secure, and self-satisfied vs. anxious, insecure, and self-pitying. The Big Five contain important dimensions of personality. However, some personality researchers argue that this list of major traits is not exhaustive. Some support has been found for two additional factors: excellent/ordinary and evil/decent. However, no definitive conclusions have been established.

John L. Holland’s RIASEC vocational model, commonly referred to as the Holland Codes, stipulates that six personality traits lead people to choose their career paths. In this circumplex model, the six types are represented as a hexagon, with adjacent types more closely related than those more distant. The model is widely used in vocational counseling.

Trait models have been criticized as being purely descriptive and offering little explanation of the underlying causes of personality. Eysenck's theory, however, does propose biological mechanisms as driving traits, and modern behavior genetics researchers have shown a clear genetic substrate to them. Another potential weakness of trait theories is that they lead people to accept oversimplified classifications, or worse offer advice, based on a superficial analysis of their personality. Finally, trait models often underestimate the effect of specific situations on people's behavior. It is important to remember that traits are statistical generalizations that do not always correspond to an individual's behavior.