Personality, reaction time, and event-related potentials.

Reaction time (RT), movement time (MT), and the amplitude and latency of the P300 event-related potential were recorded from 30 Ss during the performance of 6 simple cognitive tasks. Extraversion was negatively associated with MT, a result that endorses the view that extraversion is determined, in part, by individual differences in motor mechanisms. Higher neuroticism scores were associated with faster P300 latency, a measure that is regarded as an index of stimulus evaluation time that is independent of response production. Paradoxically, higher neuroticism scores were associated with slower RT, a measure that is also regarded as an index of speed of information processing. Higher psychoticism scores were associated with smaller P300 amplitude, an effect that may be indicative of less attentional effort invested in the tasks. The analyses of individual differences in the response to sensory stimulation and in the expression of motor responses are important sources of evidence for several proposals that have been put forward in the explanation of personality differences, notably extraversion, impulsiveness, and anxiety (Barratt, 1972; Brebner & Cooper, 1974; H. J. Eysenck, 1957; Newman, 1987; Stelmack, 1985). The present article aims to articulate differences in the processing of stimuli and production of responses that are relevant to the biological bases of those personality dimensions by exploiting relatively recent refinements in eventrelated potential (ERP) and reaction time (RT) measures that are recorded during the performance of simple cognitive tasks. This article addresses several questions that have emerged in the study of individual differences in extraversion and impulsiveness. At this time, there is a good deal of evidence from research using both behavioral and psychophysiological measures that demonstrates the greater sensory reaction to simple physical stimulation for introverts than extraverts (Stelmack, 1990). However, it is unclear whether these effects reflect differences at early stages of stimulus input, central stimulus analysis, or both. There is also a literature spanning 30 years that affirms differences between extraverts and introverts and between high- and low-impulsive subjects in their performance on various tasks that assess speed of responding and motor control (Barratt & Patton, 1983; Stelmack, 1985). Again, it is not clear whether these effects involve differences in central processing, motor response, or both. This issue is complicated because impulsiveness can be described as a complex construct composed of facets of extraversion, neuroticism, and psychoticism (H. J.