Investigating the effects of acute caffeine administration on visual search, resistance to distraction, and attentional learning.

The ability to selectively attend to task-relevant information is central to the performance of a variety of cognitive tasks. Accessible and low-risk pharmacological interventions hold promise with respect to maximizing cognitive performance and augmenting attentional abilities. Acute administration of caffeine reflects one such pharmacological intervention, which has been shown to improve some measures of attention. The effects of caffeine on the efficiency of attentional selection during visual search and the degree to which such efficiency can improve with learning have not been investigated, which we tested here. In a single-blind between-subjects design, participants received either 200 mg of caffeine or placebo and completed visual search tasks in which the target (Experiment 1) and a physically salient distractor (Experiment 2) were more likely to be rendered in a particular color. A third task was also implemented to measure the trade-off between physical and attentional effort under the effect of caffeine (Experiment 3). The efficiency of target selection (Experiment 1) and distractor rejection (Experiment 2) were strongly influenced by color-based statistical learning. Participants were sensitive to the trade-off between physical and attentional effort (Experiment 3). However, none of these measures were influenced by caffeine. A beneficial effect of caffeine was observed on the speed of target recognition in Experiment 1 only. Our findings suggest a limited role for the influence of caffeine on the attention system.