Philosophical assumptions

Many of the ideas developed by historical and modern personality theorists stem from the basic philosophical assumptions they hold. The study of personality is not a purely empirical discipline, as it brings in elements of art, science and philosophy to draw general conclusions. The following five categories are some of the most fundamental philosophical assumptions on which theorists disagree:

1. Freedom versus Determinism

This is the debate over whether we have control over our own behavior and understand the motives behind it (Freedom), or if our behavior is causally determined by forces beyond our control (Determinism). Determinism has been considered unconscious, environmental, or biological by various theories.

2. Heredity versus Environment

Personality is thought to be determined largely by either genetics and heredity, by environment and experiences, or by some combination of the two. There is evidence for all possibilities. Contemporary research suggests that most personality traits are based on the joint influence of genetics and environment.

3. Uniqueness versus Universality

The argument over whether we are all unique individuals (Uniqueness) or if humans are basically similar in their nature (Universality). Gordon Allport, Abraham Maslow and Carl Rogers were all advocates of the uniqueness of individuals. Behaviorists and cognitive theorists, in contrast, emphasized the importance of universal principles such as reinforcement and self-efficacy.

4. Active versus Reactive

Do we primarily act through our own initiative (Active), or react to outside stimuli (Reactive)? Behavioral theorists typically believe that humans are passively shaped by their environments, whereas humanistic and cognitive theorists believe that humans are more active.

5. Optimistic versus Pessimistic

Personality theories differ on whether people can change their personalities (Optimism), or if they are doomed to remain the same throughout their lives (Pessimism). Theories that place a great deal of emphasis on learning are often, but not always, more optimistic than theories that do not emphasize learning.

Personality theories

Critics of personality theory claim personality is "plastic" across time, places, moods and situations. Changes in personality may indeed result from diet (or lack thereof), medical effects, significant events, or learning. However, most personality theories emphasize stability over fluctuation.

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 Eysenck 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 analyze 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.