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Abstract
According to the Yerkes-Dodson law, performance is an inverted-U function of arousal with a negative relationship between optimal arousal and task difficulty. Both easy [letter cancellation] and difficult [verbal abilities] tasks were completed during the morning by 100 subjects differing in impulsivity; each subject was tested with five different doses of caffeine. Data were subjected to a traditional analysis of variance; in addition, data from individual subjects were analyzed. Group-level results indicated that performance was an interactive function of task, caffeine, and impulsivity [P