Extraversion is one of the most studied traits in personality psychology. Some form of the trait has been included in almost every comprehensive model of personality. At the broadest level of description, extraversion reflects the extent to which a person is interested in and enjoys social interaction. However, this broad trait also encompasses a number of more specific facets. For instance, each of the following facets has been included in at least one major model of extraversion: impulsivity, assertiveness, activity level, the tendency to engage in excitement-seeking behaviors, the experience of positive emotions, and feelings of warmth toward others. Given the relative diversity of these characteristics, it should be no surprise that psychologists disagree about which of these narrower facets is the defining feature of extraversion (or whether a defining feature even exists). Modern personality psychologists strive to resolve this debate and to understand the psychological and physiological processes that underlie this trait.
Models of Extraversion
The history of extraversion research is as long as the history of psychology itself. Precursors of the trait can be found in the writings of the ancient Greeks, though many psychologists trace the origin of modern extra-version research to Carl Jung. Jung believed that individuals varied in their orientation to the external world. Extraverts were thought to be characterized by strong and immediate reactions to the objective features of the environment. Introverts, on the other hand, were thought to be more tuned in to the internal, subjective feelings that objects in the world create. Thus, extraverts were thought to be adept at dealing with the changing external environment (and perhaps somewhat impulsive), whereas introverts were thought to be less adaptable and more prone to introspection.
Hans Eysenck built on the work of Jung (and others) and attempted to identify the processes that might underlie these extraverted thoughts and behaviors. Initially, Eysenck, like Jung, thought that extraverts were defined by their impulsivity and their tendency to react to changing external circumstances. He posited that individual differences in this characteristic were due to differential levels of excitation and inhibition. Specifically, Eysenck believed that extraverts were characterized by weak and slowly developing excitation, as well as strong and quickly developing inhibition. Thus, extraverts conditioned (or learned) slowly and got bored with repetitive tasks quickly. As a result of these underlying processes, extraverts were poorly socialized and craved changing conditions.
This initial model was found to be insufficient, and Eysenck quickly replaced it with a model based on individual differences in arousal. According to this revised model, extraverts were characterized by relatively low levels of arousal, whereas introverts were characterized by relatively high levels of arousal. Because too little or too much arousal impairs performance and is subjectively unpleasant, extraverts and introverts should seek out different types of environments. Extraverts should choose and enjoy highly arousing situations like parties or risky activities, whereas introverts should choose and enjoy more sedate activities likely spending time alone or inter-acting with a relatively small number of friends. Eysenck tested his model by examining extraverts’ and introverts’ performance in conditions that varied in their level of stimulation.
Soon after Eysenck proposed his arousal model, Jeffrey Gray developed a revised theory that was based on more detailed models of psychophysiological systems in the brain. This revised model shifted the underlying explanatory mechanism from individual differences in arousal to individual differences in sensitivity to reward. Gray believed that extraverts were highly sensitive to rewards, whereas introverts (particularly neurotic introverts) were highly sensitive to punishment. Thus, extraverts should learn better when given rewards for good performance, whereas introverts should learn better when punished for poor performance. Furthermore, extraverts were thought to be more strongly motivated to approach rewards than introverts. Recent research has focused on the role of dopamine in this reward-seeking behavior.
At the same time that Eysenck and Gray were developing their psychophysiological models of extra-version, other personality researchers were using factor-analytic techniques to determine whether a small number of basic traits could subsume and account for the many different characteristics that personality researchers had studied. For instance, researchers from the lexical hypothesis tradition posited that all important individual differences in personality would be encoded in language. Therefore, factor analyses of personality descriptors should be able to uncover any basic personality traits that exist. Other researchers set out to factor-analyze existing questionnaire items to see whether a small number of traits underlie the large number of characteristics that psychologists had studied in the past.
Over the years, these factor-analytic studies have consistently supported the idea that five broad dimensions (the Big Five) underlie much of the individual differences in personality. The first and largest factor that emerges from these analyses has been given a variety of labels including “confident self-expression,” “surgency,” “assertiveness,” and “power.” Yet even with these different names, most personality psychologists agree that this first factor usually resembles extraversion. Thus, extraversion is an important part of modern five-factor models of personality.
Correlates of Extraversion
Not surprisingly, extraversion has often been linked with social outcomes, including the amount of time that a person spends with others, the number of friends that a person has, and the extent to which a person enjoys social activities. Extraverts tend to score higher than introverts on all of these measures. However, because extraversion is a broad trait, it has also been linked with a variety of other outcomes. For instance, because of their greater impulsivity, extraverts are more likely than introverts to engage in risky behaviors (including some risky health behaviors). On the other hand, extraverts tend to be slightly more productive than introverts at work and are more likely to be involved in community activities, perhaps because of their social skills and social interest. Extraverts have also been shown to be happier than introverts and less susceptible to certain types of psychological disorders.
- Watson, D., & Clark, L. A. (1997). Extraversion and its positive emotional core. In R. Hogan, J. Johnson, & S. Briggs (Eds.), Handbook of personality psychology (pp. 767-793). San Diego, CA: Academic Press.