The effects of caffeine on reaction time in hyperkinetic and normal children.

Using a double-blind design, the authors investigated 1) caffeine's effect in hyperkinetic children on a choice reaction time task, 2) whether caffeine has different effects on simple reaction time and choice reaction time, and 3) whether its effects in the hyperkinetic compared with the normal group of children are best described by the law of initial values or as a "paradoxical effect." The results indicate that caffeine produced an increase in the accuracy of stimulus identification and processing and a decrease in lapses of attention for the hyperkinetic group. The law of initial values best represented the phenomena observed.