What Is Personality

Theories of human personality predate scientific methods. In the oldest documented examples, ancient Greek physicians at the time of Galen attributed individual differences in temperament to the balance of bodily fluids in a given individual (Siegel, 1968). Regardless of the mechanistic correctness of this explanatory framework, the

Greek physicians' observations intrigued and inspired many of the progenitors of modern experimental psychology, including Pavlov (1935) and Wundt (1896). Early in the 20th century, experimental psychologists turned their attention not only to describing individual differences in humans but also toward measuring them. While some focused on traits related to intelligence (Binet, 1905), others focused on traits related to emotional and social functioning.

Allport emphasized both the content and organization of these socioemotional traits when he defined personality as: "the dynamic organization within the individual of those psychophysical systems that determine characteristics of behavior and thought." Although traditionally, "temperament" referred to "immature" traits of biological origin while "character" referred to "mature" traits that have been sculpted by socialization, Allport included both types of traits under the rubric of "personality," due to concerns about moral or evaluative connotations of a distinction between temperament and character (Allport, 1961). His decision not to distinguish the two proved empirically prescient since recent studies suggest that both putatively "temperamental" and "characterological" traits share comparable degrees of heritability (Plomin et al., 1990), and indices purporting to measure each separately are often intercorrelated (Cloninger et al., 1993; Herbst et al., 2000).

Psychometric studies that followed Allport's early formulations (Allport and Odbert, 1936) helped to lay the foundation for current personality theory. Specifically, scientists began to employ factor analysis as a means of determining the underlying structure or dimensionality of peoples' personality descriptions of themselves and others. Some researchers randomly sampled descriptors from bodies of spoken or written language (e.g., dictionaries) while others selected descriptors on the basis of theory. Although resulting models of personality sometimes contained different numbers of factors, all of the models relevant to personality disorders tend to share a handful of common factors.

One such model was developed by Leary and colleagues and based on Sullivan's theory of interpersonal behavior (Freedman et al., 1951). This "interpersonal circum-plex" model describes personality in terms of two independent dimensions: dominance and affiliation. An example of an instrument used to measure self-rated interpersonal descriptions is the Interpersonal Adjective Scales—Revised (Wiggins et al., 1988), and a second instrument that measures interpersonal problems is the Inventory of Interpersonal Problems (Horowitz et al., 1988). More recent extensions of this model that have been used to assess personality disorder symptomatology include the Structural Analysis of Social Behavior, developed by Benjamin and colleagues (Benjamin, 1996).

A second model that focused more on the individual than on his or her social interactions was proposed by Eysenck, who was inspired by Pavlov's observations of individual differences in the behavior of dogs as they learned to discriminate between different incentive cues (Eysenck, 1987). This "PEN" model described personality in terms of three dimensions: psychoticism, extraversion, and neuroticism. A modern extension of Eysenck's model (Costa and McCrae, 1992) also reflected the findings of extensive factor analytic studies of personality descriptors in the English language (Goldberg, 1990). This "five-factor model" (a.k.a. the "big 5") described personality in terms of five dimensions: extraversion, neuroticism, openness, agree-ableness, and conscientiousness. A currently popular instrument for measuring these five factors in healthy individuals is the NEO Personality Inventory, Revised (NEO-PIR; Neuroticism-Extraversion-Openness Personality Inventory, Revised) (Costa and McCrae, 1992). Investigators have also developed the Structured Interview for the Five-Factor Model of Personality (SIFFM) to assess these five factors in personality-disordered individuals (Trull and Widiger, 1997).

Subsequent research and analyses have verified that some factors from the five-factor model map both onto factors in the interpersonal circumplex and the PEN model in healthy individuals. Specifically, low extraversion corresponds with the low dominance/low affiliation quadrant of the interpersonal circumplex, while low agreeableness corresponds with the high dominance/low affiliation quadrant of the interpersonal circumplex (Costa and McCrae, 1989). Additionally, as one might predict based on the derivation of the NEO from Eysenck's PEN model, high NEO-PIR extraversion corresponds with high PEN extraversion, high NEO-PIR neuroticism corresponds with high PEN neuroticism, and low NEO-PIR agreeableness corresponds with high PEN psychoticism (see Table 5.2). Despite differences in the derivation and construction of these measures, this convergence suggests that decades of psychometric research have led to a remarkable consensus regarding the basic structure of personality traits (Digman, 1990). Four of the five factors (all but openness) have repeatedly been replicated in cross-cultural comparisons (De Raad et al., 1998), and each shows prominent heritable components in twin and adoption studies (30 to 50 percent) (Bouchard, 1994; Bouchard and Loehlin, 2001). Thus, these four traits probably reflect the operation of integrated "psychophysical systems" (a la Allport), rather than culturally acquired semantic biases (Passini and Norman, 1966).

Anxiety and Depression 101

Anxiety and Depression 101

Everything you ever wanted to know about. We have been discussing depression and anxiety and how different information that is out on the market only seems to target one particular cure for these two common conditions that seem to walk hand in hand.

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