Abstract
The present study examined caffeine's effect on mental performance in contrast to a recent study (Loke and Goh, 1992) which examined the effects of caffeine user‐effect on mental performance. Taken together, the studies would provide a detailed understanding of the effects of caffeine and automaticity on the visual search/detection domain of information processing. Analyses of the baseline measures of the visual search/detection task showed significant differences between low and high levels of automaticity and levels of task difficulty. Performance on the low difficulty level was higher than the high difficulty level, and performance on automatic task was higher than on non‐automatic task. Caffeine, however, did not interact with automaticity and task difficulty. Therefore, given that the present study used unpractised (novice) subjects with similar levels of caffeine consumptions and personality characteristics, the visual search/detection domain of information processing is shown to be insensitive to the effects of caffeine. This supports the general view that caffeine does not affect cognition, learning, and memory performance. Also, the non‐significant three‐way interaction of drug, automaticity, and task difficulty would therefore suggest that caffeine does not affect resource capacity. Of note is that knowledge of drug administration assessments (drug guessing) was sensitive to the effects of caffeine in the automatic condition and not in the non‐automatic condition, suggesting that the effects of caffeine are task‐dependent. In contrast, the expected sensitivity of mood assessments to caffeine's effects was not shown. Since caffeine is shown to be a ‘weak’ stimulant, given its commonly known non‐significant effects on mental performance, caffeine‐administered subjects may lack sufficient external cues to allow them to perceive and report correctly that they were given caffeine.