Trait theory

Trait theory is an approach to personality theory in psychology.

The emotions, thoughts and behavior patterns that a person has are typically referred to as a personality (Kassin, 2003) and can vary immensely between individuals. In making the area amenable to scientific enquiry some, using the statistical technique of factor analysis, have hypothesized that the personality contains prominent aspects that are stable across situations called shamonetraits. In particular, Eysenck (1967,1991) has suggested that personality is reducible to three major traits (3F), though others (e.g. McCrae and Costa, 1987) have suggested there are five (5F). There are other proponents who suggest there are more factors than this (e.g. Saucier and Goldberg, 1998; Raymond Cattell, 1970).

How the Taxonomy is Defined
The 3F model is comprised of the traits, ‘extraversion’, ‘neuroticism’ and ‘psychoticism’ but the 5F models contains ‘openness’, ‘conscientiousness’, ‘extraversion’, ‘agreeableness’ and ‘neuroticism’. These traits exist because they are the highest-level factors of a hierarchical taxonomy based on the statistical technique factor analysis. They are the result of factor analysis on lower-order traits which themselves are the product of factor analysis on habits which in turn exist because of factor analyses on behaviours. Indeed, such a method produces factors that are continuous, bipolar, can be distinguished from states and can describe individual differences (Goldberg, 1993). Indeed, both approaches use self-report questionnaires to try and capture the top-level factors by means of the lower levels. However, although they use broadly the same methodology there are some differences. Firstly, the nature of the questionnaires are subtly different; for example, 3F uses a binary answering system of ‘yes’ and ‘no’ while 5F use a five-point scale. Secondly, there are organisational differences; for instance, the 3F model is strict in as much as a four tier hierarchy is adhered to and the three top-level factors are intended to be orthogonal (uncorrelated) (Eysenck, 1990), although Eysenck & Eysenck (1991) found small positive correlations between psychoticism and the two other traits particularly in males. Conversely, the 5F model has been criticized for mixing up these levels and corrupting the orthogonal relationships (Block, 1995; Draycott and Kline, 1995). Eysenck (1992a) argued that fewer factors were superior to a larger number of partly related ones. Thus while the two approaches are comparable because of the use of factor analysis to construct hierarchical taxonomies they differ in their setup. In particular, there are differences in the organization and number of high-level factors. However there are similarities and differences between lower-order factors too.

Lower Order Factors


There are two top level factors that both approaches agree on: 'extraversion' and 'neuroticism'. Both approaches broadly accept that extraversion is associated with sociability and positive affect while neuroticism is associated with emotional instability and negative affect (Matthews, Deary & Whiteman, 2003). Indeed, many of the lower-order factors employed are similar. For instance, both approaches contain a factor for sociability/gregariousness, for activity levels and for assertiveness for the high-order factor 'extraversion'. However, there are differences too. First, the 3F approach contains nine lower-order factors and the 5F approach has six (Matthews et al., 2003), which is a generalized difference between the two approaches. More specifically, the lower-order factors differ between high-order factors. For instance, within 'extraversion' the 3F approach includes ‘carefree’ as a factor but the 5F approach makes no such reference. Similarly, there are differences within 'neuroticism', with ‘guilt’ as a factor in the 3F approach but not in the 5F approach. The pattern that emerges is that the 3F approach is more willing to condense more lower-order factors into fewer high-order factors. In fact, such a pattern is true when other high-order factors are examined. For instance, 'psychoticism' incorporates some of the polar opposites of the lower-order factors of ‘openness’, ‘agreeableness’ and ‘conscientiousness’ (Matthews et al., 2003). A high scorer on tough-mindedness in ‘psychoticism’ would score lowly on tender-mindedness in ‘agreeableness’ (see image below for more examples). Therefore, while the two approaches contain similarities in their lower-level factors there are also large differences. In particular, most of the differences stem from the 3F approach’s emphasis on fewer high-order factors, which means many of the low-order factors for ‘psychoticism’ are observable in the lower order factors of the 5F approach and vice versa.

Causal Claims
So far it has been shown that the two approaches tend to be comparable and differ in their organization of factors. However, the two approaches differ in their causal claims. While both models are descriptive only the 3F offers any detailed causal explanations and this sets the two approaches apart. Though Costa and McCrae (1992) have suggested that traits are a mixture of environment and genetics, the 3F approach suggests explicitly that different personality traits are caused by the properties of the brain, which themselves are the result of genetic factors (Eysenck and Eysenck, 1985). In particular, the 3F model identifies the reticulo-cortical and reticulo-limbic circuits in the brain as key parts of the conceptual nervous system with the specific functions of mediating cortical arousal and emotional responses respectively. Eysenck (1967) advocates that extroverts have low levels of cortical arousal and introverts have high levels, leading extroverts to seek out more stimulation from socialising and being venturesome. Moreover, Eysenck (1994) surmised that there would be an optimal level of arousal after which inhibition would occur and that this would be different depending where on the factor continuum a person was. In a similar vein, the 3F approach theorizes that the factor neuroticism is mediated by levels of arousal in the limbic circuit with individual differences arising because of variable activation thresholds between people. Therefore, highly neurotic people when presented with minor stressors will exceed this threshold, while very weakly neurotic people would not exceed idiosyncratic activation levels even when presented with large stressors. The individual differences in both extraversion and neuroticism according to the 3F approach have genetic and physiological antecedents. By contrast, proponents of the 5F approach assume a role of genetics and environment but offer no explicit causal information.

Given this emphasis on biology in the 3F approach it would be expected that the third trait, psychoticism, would have a similar explanation. However, the causal properties of this state are not well defined. Eysenck (1992b) has suggested that psychoticism was related to testosterone levels and was inverse function of the serotonergic system but later revised this (Eysenck, 1997) linking it instead to the dopaminergic system. Whatever the causes, however, psychoticism marks the two approaches apart as the 5F model contains no such trait, although as has been demonstrated, it can be viewed as an amalgam of factors in the 5F approach. Moreover, apart from simply being a different high-level factor ‘psychoticism’, unlike any of the other factors in either approach does not fit a normal distribution curve. Indeed, scores are rarely high thus skewing a normal distribution (Matthews, et al., 2003). However, when they are high there is considerable overlap with psychiatric conditions such as antisocial and schizoid personality disorders. Similarly, high scorers on ‘neuroticism’ are more susceptible to sleep and psychosomatic disorders (Eysenck and Eysenck, 1991). Although 5F approaches can predict future mental disorders (e.g. Costa & McCrae, 1990, Lynam et al, 2005) it is important to note that the motivation for such a model was primarily taxonomic. Although ‘psychoticism’ may contain lower-order factors from the 5F approach and although ‘neuroticism’ is a higher-order factor in both approaches, the 3F model stands alone as a model created with the aim of predicting for psychiatric disorders, like psychosomatism or psychosis (Heath and Martin, 1990). That said, Eysenck and Eysenck (1991) contend that ‘psychoticism’ and ‘neuroticism’ are typical traits in individuals. Therefore, the high-order factor ‘psychoticism’ like others in the 3F approach is suggested to have (rather unspecified) biological causes, which although uneven distributed in a population are normal according the 3F approach. Moreover, while both approaches can be used as predictive tools the 3F approach was the first to notice this.

Summary
The debate between three- and five-factor approaches to understanding personality has been perhaps the largest in all individual differences research and for good reason. The two approaches are in many ways identical: for instance, in their use of hierarchical factor analysis, their use of traits themselves as continuous, bipolar dimensions of personality, the questionnaires used to capture the essence of such traits, the emphasis on taxonomy, the sharing of two important traits and the similar organisation of many of the lower-level factors. However, the differences are typically subtle ones. Contrasts can be made between the answering style in the questionnaires, the organisation and number of the lower-order factors, the emphasis of the three factor approach to condense more into less though the five factor approach is content with more and also the predictive claims made by the 3F approach. However, perhaps the most marked difference is that of causality. The 5F approach focuses on taxonomy and suggests that both nature and nurture are important causal factors, but that the former should be developed before any work should be done on the latter. By contrast, the three-factor approach assumes the differences arise from physiology, defined by genetics. For individual differences in typical humans the 5F approach is probably better operationally as it is more nuanced and theoretically because it assumes more liberal causal factors; however, such an approach would never have been possible without the work into 3F approach.