Personality Traits
One of the pioneering trait psychologists, Gordon Allport (1937), saw traits as organised mental structures, varying from person to person, which initiate and guide behaviour. There are two important qualifications to this general principle. First, as Hettema and Deary (1993) pointed out, the explaining of behaviour requires different levels of analysis, including genetics, physiology, learning and social factors. Allport's notion that all the various manifestations of traits can be explained at a single level of 'mental structure' is simplistic. Hence, causal models of trait action will vary depending on the level investigated, although the ultimate research aim is to develop a trait theory that will connect various levels. Second, the causal effects of traits on behaviour may be indirect. Traits interact with situational factors to produce transient internal conditions or states, which may sometimes be a more direct influence on behaviour than the trait. For example, trait anxiety may interact with an immediate situational threat to generate transient state anxiety, which in turn disrupts ongoing information processing and impairs performance (Spielberger, 1966).
Tendency to experience negative emotions are assumed by some to relate to some fundamental, core quality of the person, which might be influenced substantially by genetic factors (Eysenck, 1967; McCrae et al., 2000). Again, even within theories that are sympathetic to the traditional view of traits, there has been some modification of the basic view. For example, Cattell and Kline (1977) distinguished 'surface' traits, which are simply clusters of overt responses which tend to be associated, from 'source' traits, which are deeper properties of the person with causal effects on behaviour. Modern developments of traditional theory seek to identify and explain underlying sources of consistency in behaviour, whether these are conceived of as genetic, physiological or...