Introduction to personality psychology

Personality psychology is a branch of psychology which studies personality and individual different processes - that which makes us into a person. One emphasis is on trying to create a coherent picture of a person and all his or her major psychological processes. Another emphasis views it as the study of individual differences. These two views work together in practice. Personality psychologists are interested in a broad view of the individual. This often leads to an interest in the most visible individual differences among people.

What is personality?
In psychology, personality is a collection of emotional, thought and behavioral patterns unique to a person. The word originates from the Latin persona, which means "mask."

A typology of personality models
Modern personality models may generally be broken into three types: factorial models, typologies and circumplexes.

Factorial models posit that there are dimensions along which human personality differs. The main purpose of a personality model is thus to define the dimensions of personality. Factor analysis is a primary tool of theorists composing factorial models. Such models arise directly from a classical individual differences approach to the study of human personality. Goldberg's Big Five model described below may be the best-known example of this type of theory.

Typologies or type models arise naturally from some theories that posit types of people. For example, astrological signs represented a well-known, pre-scientific typological model. Typological models posit a relatively small number of modal types and possibly some interaction between the types. The Jungian typology implemented in the MBTI and discussed below may best represent the typology approach.

Circumplex models may resemble factorial or type models but further specify a relationship between the different types or factors. Typically, some types or factors are more related than others and can be presented on a polygon. John L. Holland's RIASEC or Holland Codes (see below) may be the best-known example of this type of theory. Correlations of personality scores should resemble a simplex form where opposing types have low correlation and close types have a high correlation.

Personality theories
There are several theoretical perspectives on personality in psychology, which involve different ideas about the relationship between personality and other psychological constructs, as well as different theories about the way personality develops. Most theories can be grouped into one of the following classes.

Trait theories
According to the Diagnostic and Statistical Manual of the American Psychiatric Association, personality traits are "prominent aspects of personality that are exhibited in a wide range of important social and personal contexts." In other words, persons have certain characteristics which partly determine their behaviour. According to the theory, a friendly person is likely to act friendly in any situation because of the traits in his personality. One criticism of trait models of personality as a whole is that they lead professionals in clinical psychology and laypeople alike to accept classifications, or worse offer advice, based on superficial analysis of one's profile.

The most common models of traits incorporate four or 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).

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 * 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." A different model was proposed by Hans Eysenck, who believed that 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 subject 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) Extroversion (i.e., "extroversion vs. introversion" above; outgoing and physical-stimulation-oriented vs. quiet and physical-stimulation-averse)
 * 2) Neuroticism (i.e., emotional stability; calm, unperturbable, optimistic vs. emotionally reactive, prone to negative emotions)
 * 3) Agreeableness (i.e., affable, friendly, conciliatory vs. aggressive, dominant, disagreeable)
 * 4) Conscientiousness (i.e., dutiful, planful, and orderly vs. spontaneous, flexible, and unreliable)
 * 5) Openness to experience (i.e., open to new ideas and change vs. traditional and staid)


 * John L. Holland's RIASEC vocational model, commonly referred to as the Holland Codes, stipulates that 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.


 * Building on the writings and observations of Carl Jung, during WWII Isabel Briggs Myers and her mother Katharine C. Briggs delineated personality types by constructing the Myers-Briggs Type Indicator. This model was later elaborated further by David Keirsey. It is an older, more theoretically-motivated, but quite popular approach to personality traits and is also called the Big Four model, accepting Extroversion vs. Introversion as basic and adding an additional three:
 * 1) Extroversion vs. Introversion (see above)
 * 2) Intuition vs. Sensing (trust in conceptual/abstract models of reality versus concrete sensory-oriented facts)
 * 3) Thinking vs. Feeling (thinking as the prime-mover in decision-making vs. feelings as the prime-mover in decision-making)
 * 4) Perceiving vs. Judging (desire to perceive events vs. desire to have things done so judgements can be made)


 * 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 intuition factor is considered the most basic, dividing people into "N" or "S" personality types. An "N" is further assumed to be guided by the thinking or objectication habit, or feelings, and be divided into "NT" (scientist, engineer) or "NF" (author, human-oriented leader) personality. An "S", by contrast, is assumed to be more guided by the perception axis, and thus divided into "SP" (performer, craftsman, artisan) and "SJ" (guardian, accountant, bureaucrat) personality. These four are considered basic, with the other two factors in each case (including always extraversion) less important. Critics of this traditional view have observed that the types are quite strongly stereotyped by professions, and thus may arise more from the need to categorize people for purposes of guiding their career choice. This among other objections led to the emergence of the five factor view, which is less concerned with behavior under work stress 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").

Psychoanalytic theories
Psychoanalysis theories explain human behaviour in terms of interaction between the various components of personality. Sigmund Freud was the founder of this school. Freud drew on the physics (thermodynamics) of his day to coin the term psychodynamics: based on the popular ideas of conversion of heat into mechanical energy and vice versa, he proposed the conversion of psychic energy into behaviour. He broke the human personality down to three significant components: the ego, superego, and id. According to Freud, personality is shaped by the interactions of these three components.

Behaviorist theories
Behaviorists explain personality in terms of reactions to external stimuli. This school of thought was initiated by B. F. Skinner. According to these theories, people's behaviour is formed by processes such as operant conditioning.

Cognitive and social-cognitive theories
In cognitivism behaviour is explained as guided by cognitions (e.g. expectations) about the world, and especially those about other people. Albert Bandura, a social learning theorist suggested that the forces of memory and emotions worked in conjunction with environmental influences.

Humanistic theories
In humanistic psychology it is emphasized people have free will and that they play an active role in determining how they behave. Accordingly, humanistic psychology focuses on subjective experiences of persons instead of factors that determine behaviour. Abraham Maslow and Carl Rogers were proponents of this view.

Other theories
There are many other views on personality psychology, one of them George Kelly's personal construct psychology. Other important contributors to the field are Anna Freud, Erik Erikson, Otto Rank, Alfred Adler, Karen Horney, Albert Ellis, Erich Fromm, Hans Eysenck, Snygg and Combs, Ludwig Binswanger, Medard Boss, Viktor Frankl, Rollo May, and Jean Piaget. The fields of evolutionary psychology and Buddhist Psychology are also of interest in this context.

Personality tests
Types of personality tests include the Holland Codes, the Rorschach test, the Minnesota Multiphasic Personality Inventory, the Myers-Briggs Type Indicator, NEO PI-R, and the Thematic Apperception Test. Critics have pointed to the Forer effect to suggest that some of these appear to be more accurate and discriminating than they really are.

Personality psychology is often closely associated with social psychology.

Brain Research
Around the 1990s, neuroscience entered the domain of personality psychology. Whereas previous efforts for identifying personality differences relied upon simple, direct, human observation, neuroscience introduced powerful brain analysis tools like Electroencephalography (EEG), Positron Emission Tomography (PET), and Functional Magnetic Resonance Imaging (fMRI) to this study. One of the founders of this area of brain research is Richard Davidson of the University of Wisconsin-Madison. Mr. Davidson's research lab has focused on the role of the prefrontal cortex (PFC) and amygdala in manifesting human personality. In particular, this research has looked at hemispheric asymmetry of activity in these regions.

In December 2005, a self-described "hacker" posted, for free download, a partially finished book entitled "Personality and the Brain". This book, which relies in part on the research of Mr. Davidson, hypothesizes that the Enneagram theory of human personality appears supported by the emerging findings of neuroscience. In particular, this book relies on studies concerning PFC and amygdala asymmetry. As of December 2005, however, this book's hypothesis had not yet been tested.