Philosophical assumptions

Many of the ideas developed by historical and modern personality theorists stem from the basic philosophical assumptions they hold. A good textbook for understanding basic assumptions behind personality theories is Hjelle and Ziegler (1992). This book is now out of print, but similar views are articulated by Ryckman (2000). 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
See also: Free will

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 to be unconscious, environmental, or biological by various theories.

2. Heredity versus Environment
Main article: Nature versus nurture

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 do we 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 vs. 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, who 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": 
Extraversion - outgoing and stimulation-oriented vs. quiet and stimulation-avoiding
Neuroticism - emotionally reactive, prone to negative emotions vs. calm, imperturbable, optimistic
Agreeableness - affable, friendly, conciliatory vs. aggressive, dominant, disagreeable
Conscientiousness - dutiful, planful, and orderly vs. laidback, spontaneous, and unreliable
Openness to experience - open to new ideas and change vs. traditional and oriented toward routine
For ease of remembrance, this can be written as either OCEAN or CANOE.
John L. Holland's RIASEC vocational model, commonly referred to as the Holland Codes, stipulates there are six personality traits that lead people to choose their career paths. This model is widely used in vocational counseling and is a circumplex model where the six types are represented as a hexagon where adjacent types are more closely related than those more distant.

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 demonstrated a clear genetic substrate to them.[vague] Another potential weakness with trait theories is they lead people to accept oversimplified classifications, or worse offer advice, based on a superficial analysis of one's personality. Finally, trait models often underestimate the effect of specific situations on people's behavior. It is important to remember traits are statistical generalizations that do not always correspond to an individual's behavior.


Type theories

Personality type refers to the psychological classification of different types of people. Personality types are distinguished from personality traits, which come in different levels or degrees. According to type theories, for example, there are two types of people, introverts and extraverts. According to trait theories, introversion and extraversion are part of a continuous dimension, with many people in the middle. The idea of psychological types originated in the theoretical work of Carl Jung[citation needed] and William Marston, whose work is reviewed in Dr. Travis Bradberry's The Personality Code. Jung's seminal 1921 book on the subject is available in English as Psychological Types.

Building on the writings and observations of Carl Jung, during World War II, Isabel Briggs Myers and her mother, Katharine C. Briggs, delineated personality types by constructing the Myers-Briggs Type Indicator.[2] This model was later used by David Keirsey with a different understanding from Jung, Briggs and Myers.[3] In the former Soviet Union, Lithuanian Aušra Augustinavičiūtė independently derived a model of personality type from Jung's called Socionics.

The model is an older and more theoretical approach to personality, accepting extraversion and introversion as basic psychological orientations in connection with two pairs of psychological functions:
Perceiving functions: sensing and intuition (trust in concrete, sensory-oriented facts vs. trust in abstract concepts and imagined possibilities)
Judging functions: thinking and feeling (basing decisions primarily on logic vs. considering the effect on people).

Briggs and Myers also added another personality dimension to their type indicator to measure whether a person prefers to use a judging or perceiving function when interacting with the external world. Therefore they included questions designed to indicate whether someone wishes to come to conclusions (judgment) or to keep options open (perception).[2]

This personality typology has some aspects of a trait theory: it explains people's behaviour in terms of opposite fixed characteristics. In these more traditional models, the sensing/intuition preference is considered the most basic, dividing people into "N" (intuitive) or "S" (sensing) personality types. An "N" is further assumed to be guided either by thinking or feeling, and divided into the "NT" (scientist, engineer) or "NF" (author, humanitarian) temperament. An "S", by contrast, is assumed to be guided more by the judgment/perception axis, and thus divided into the "SJ" (guardian, traditionalist) or "SP" (performer, artisan) temperament.[3] These four are considered basic, with the other two factors in each case (including always extraversion/introversion) less important. Critics of this traditional view have observed that the types can be quite strongly stereotyped by professions (although neither Myers nor Keirsey engaged in such stereotyping in their type descriptions[2][3]), and thus may arise more from the need to categorize people for purposes of guiding their career choice.[4] This among other objections led to the emergence of the five factor view, which is less concerned with behavior under work conditions and more concerned with behavior in personal and emotional circumstances. Some critics have argued for more or fewer dimensions while others have proposed entirely different theories (often assuming different definitions of "personality").

Type A personality: During the 1950s, Meyer Friedman and his co-workers defined what they called Type A and Type B behavior patterns. They theorized that intense, hard-driving Type A personalities had a higher risk of coronary disease because they are "stress junkies." Type B people, on the other hand, tended to be relaxed, less competitive, and lower in risk. There was also a Type AB mixed profile. Dr. Redford Williams, cardiologist at Duke University, refuted Friedman’s theory that Type A personalities have a higher risk of coronary heart disease; however, current research indicates that only the hostility component of Type A may have health implications. Type A/B theory has been extensively criticized by psychologists because it tends to oversimplify the many dimensions of an individual's personality.

Personality psychology

Personality psychology is a branch of psychology that studies personality and individual differences. One emphasis in this area is to construct a coherent picture of a person and his or her major psychological processes (Bradberry, 2007)[1]. Another emphasis views personality as the study of individual differences, in other words, how people differ from each other. A third area of emphasis examines human nature and how all people are similar to one other. These three viewpoints merge together in the study of personality.

Personality can be defined as a dynamic and organized set of characteristics possessed by a person that uniquely influences his or her cognitions, motivations, and behaviors in various situations (Ryckman, 2004). The word "personality" originates from the Latin persona, which means mask. Significantly, in the theatre of the ancient Latin-speaking world, the mask was not used as a plot device to disguise the identity of a character, but rather was a convention employed to represent or typify that character.

The pioneering American psychologist, Gordon Allport (1937) described two major ways to study personality, the nomothetic and the idiographic. Nomothetic psychology seeks general laws that can be applied to many different people, such as the principle of self-actualization, or the trait of extraversion. Idiographic psychology is an attempt to understand the unique aspects of a particular individual.

The study of personality has a rich and varied history in psychology, with an abundance of theoretical traditions. The major theories including dispositional (trait) perspective, psychodynamic, humanistic, biological, behaviorist and social learning perspective. There is no consensus on the definition of "personality" in psychology. Most researchers and psychologists do not explicitly identify themselves with a certain perspective and often taken an eclectic approach. Some research is empirically driven such as the "Big 5" personality model whereas other research emphasizes theory development such as psychodynamics. There is also a substantial emphasis on the applied field of personality testing.