A converging measures test of Eysenck's biologically-based theory of introversion-extraversion /

Abstract

Eysenck's (1967) theory of introversion-extraversion postulates that brainstem reticular arousal differences are the source of behavioral and performance differences between introverts and extraverts. The present study tested Eysenck's theory utilizing the convergent measurement of electroencephalographic, performance, and psychometric indices of arousal.

Twelve introverts and twelve extraverts, classified using the Eysenck Personality Inventory extraversion scale, had their brainstem auditory evoked responses (BAERs) monitored under three levels of caffeine administration (0.0 mg/kg, 1.5 mg/kg, and 3.0 mg/kg) and three levels of task demand (resting, simple reaction time, and complex reaction time).

Results indicated main effects for the personality, caffeine and task manipulations upon wave components of the BAER and speed of responding on the reaction time tasks. Several interactions were also evident between the three factors for components on the BAER and speed of responding on the reaction time tasks. The use of Thayer's (1967) Activation-Deactivation Checklist, and an independent measure of self-perceived boredom and arousal, confirmed the arousal inducing properties of the caffeine and task manipulations, but did not reveal any personality differences in subjectively felt arousal.