Extraversion is a broad, multifaceted trait, yet researchers are still unsure of its defining characteristics. One possibility is that the essential feature of extraversion is the tendency to enjoy social situations. An alternative possibility is that extraversion represents sensitivity to rewards and the tendency to experience pleasant affect. In three studies, participants rated situations that varied on two dimensions: (a) whether they were social or nonsocial and (b) whether they were very pleasant, moderately pleasant, moderately unpleasant, or very unpleasant. Extraverts only rated social situations more positively than introverts did when the situations were pleasant, and extraverts also rated nonsocial situations more positively than introverts did if the situations were pleasant. Thus, the pleasantness of situations was more important than whether they were social or nonsocial in determining extraverts' and introverts' enjoyment.

By developing a taxonomic model of personality traits, personality theorists hope to identify the “essential elements” of personality—elements that Goldberg (1981) suggested are analogous to the chemical elements in the periodic table. Specific traits could then be understood in terms of locations on a small number of broad dimensions, and personality theory could advance through the investigation of the commonalities among traits that are located along the same dimensions. For example, the knowledge that individuals who are sociable and fun-loving also tend to be dominant, active, and spontaneous (Johnson & Ostendorf, 1993) may inform our study of the processes that underlie sociable, fun-loving, dominant, active, and spontaneous behaviors.