Caffeine differentially affects kinesthetic aftereffect in high and low impulsives.

The effects of caffeine on kinesthetic aftereffect (KAE) were examined. Following a between-subjects design, high and low impulsive male postgraduate students were administered placebo and four doses of caffeine (1, 2, 3 and 4 mg/kg body weight) in a laboratory situation. A double blind procedure was adopted for drug administration. The study supports the following conclusions: (1) caffeine reduces KAE in high impulsive subjects; (2) the larger dose of caffeine (4 mg/kg) enhances KAE in low impulsive subjects; (3) caffeine produces profound effects on the performance of high impulsives; (4) caffeine leads to different dose-response trends in the two groups.