SOCIABILITY IMPULSIVITY AND CAFFEINE-INDUCED AROUSAL - CRITICAL FLICKER FUSION FREQUENCY AND PROCEDURAL LEARNING

The influence of sociability/impulsivity in caffeine-induced arousal e ffects was investigated in two separate experiments: Experiment 1 exam ined critical flicker/fusion frequency change scores (Delta CFFT) in 6 0 subjects; and Experiment 2 investigated procedural learning in 30 su bjects. In the two experiments, subjects received either caffeine citr ate (500 mg) or placebo. The pattern of results was consistent across both studies: (1) a strong interactive effect of sociability (as measu red by the EPQ extraversion scale) by caffeine/placebo which showed th at (a) subjects low in sociability showed the greatest increase in Del ta CFFT and learned most under placebo, while the reverse was true und er caffeine; (b) subjects high in sociability, showed no increase in D elta CFFT and learned least under placebo, while the reverse was true under caffeine; and (2) in neither experiment did impulsivity (as meas ured by the EPS impulsiveness scale) significantly interact with caffe ine/placebo. The results are consistent with Eysenck's (The Biological Basis of Personality, 1967) theory of personality in suggesting that subjects low in sociability are highly arousable under low-arousal (pl acebo) but over-aroused under high-arousal (caffeine), with the revers e pattern of effects holding for subjects high in sociability. The imp lications of these data for the respective roles of sociability and im pulsivity components of extraversion in arousal-mediated performance a re discussed.