Biopsychological foundations of extraversion: 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 better explained by the assumption that these two groups have differential ability to adapt their individual levels of arousal to situational demands 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 studied in the context of a major project. It was suggested that the regulatory 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 theory (Sanders, 1983). In initial studies (a memory search task and a vigilance task), within-task and between-tasks sensitivity as defined by Kahneman's adequacy criteria for indicators of psychophysiological effort were substantiated for important indices of this effort system (event-related theta, P300). The present paper reports on two studies in which Kahneman's third criterion-the sensitivity to between-subjects differences-was examined for the indicators of effort. In the first Study 23 individuals scoring high or low on the extraversion scale of the Eysenck Personality Inventory (EPI) performed a 40-minute auditory vigilance task (oddball) involving successive discrimination and a high event rate. The results supported assumptions of significant group difference across effort indicators, i.e. a significantly higher P300 amplitude among the introverts(differential effort reactivity). As task difficulty was very low in Study 1, no group differences between performance parameters appeared. Besides replication of the psychophysiological 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 vigilance task (oddball) a high level of task difficulty was set. Thirty-one introverts and extraverts scoring high or low on the EPI-E-Scale performed the task. Again, a larger P300 amplitude for introverts than for extraverts was obtained, supporting our interpretation of that parameter as an indicator for differential effort reactivity. Additionally, group differences were found in the performance domain: Extraverts showed a lower beta (decision criterion) than introverts. These results speak for the conceptualization of the effort concept in terms of the neuropsychologically specified control theory of arousal. Copyright (C) 1996 Elsevier Science Ltd.