BIOPSYCHOLOGICAL FOUNDATIONS OF EXTROVERSION - DIFFERENTIAL EFFORT REACTIVITY AND THE DIFFERENTIAL P300 EFFECT

Recent approaches of a control theory of arousal suggest that typical differences in the performance of extraverts and introverts may be bet ter explained by the assumption that these two groups have differentia l ability to adapt their individual levels of arousal to situational d emands by effortful response (differential effort reactivity) than by the assumption that these differences stem from dispositional factors of arousability or habitual arousal levels. Such an assumption was stu died in the context of a major project. It was suggested that the regu latory system (effort) presupposed by the control theory of arousal be specified on the basis of the neuropsychological theory of attention (Pribram & McGuiness, 1975) and the cognitive-energetic performance th eory (Sanders, 1983). In initial studies (a memory search task and a v igilance task), within-task and between-tasks sensitivity as defined b y Kahneman's adequacy criteria for indicators of psychophysiological e ffort were substantiated for important indices of this effort system ( event-related theta, P300). The present paper reports on two studies i n which Kahneman's third criterion-the sensitivity to between-subjects differences-was examined for the indicators of effort. In the first S tudy 23 individuals scoring high or low on the extraversion scale of t he Eysenck Personality Inventory (EPI) performed a 40-minute auditory vigilance task (oddball) involving successive discrimination and a hig h event rate. The results supported assumptions of significant group d ifference across effort indicators, i.e. a significantly higher P300 a mplitude among the introverts(differential effort reactivity). As task difficulty was very low in Study 1, no group differences between perf ormance parameters appeared. Besides replication of the psychophysiolo gical results Study 2 aimed at extending the explanatory power of the concept of differential effort reactivity of extraverts and introverts to the typical performance differences of these groups. In a visual v igilance task (oddball) a high level of task difficulty was set. Thirt y-one introverts and extraverts scoring high or low on the EPI-E-Scale performed the task. Again, a larger P300 amplitude for introverts tha n for extraverts was obtained, supporting our interpretation of that p arameter as an indicator for differential effort reactivity. Additiona lly, group differences were found in the performance domain: Extravert s showed a lower beta (decision criterion) than introverts. These resu lts speak for the conceptualization of the effort concept in terms of the neuropsychologically specified control theory of arousal. Copyrigh t (C) 1996 Elsevier Science Ltd.