CAFFEINE AND VISUOSPATIAL ATTENTION

The effects of two doses of caffeine (1.5 and 3 mg/kg) on various aspe cts of visual selective attention were investigated in 24 healthy huma n subjects. Specific task conditions were compared to provide measures of selectivity for a location in the visual field, of distractibility , of selectivity among response alternatives, and of strategic influen ces. In two out of three tasks, caffeine speeded responses significant ly. However, these effects did not differ across conditions within-tas k, so there was no indication that they were to due to (a) specific ef fect(s) on one or more of the attentional sub-functions. The results s uggest that the beneficial effects of caffeine in low-load conditions cannot be attributed to reduced distractibility or increased suppressi on of task-irrelevant response tendencies.