Caffeine enhances working memory for extraverts.

Using a randomized double-blind placebo-controlled design we examined the effects of caffeine on working memory (WM) as a function of extraverted personality. Participants (N=59) received 200mg of caffeine and placebo in counterbalanced-order over two sessions prior to completing a 'N-Back' WM paradigm. Findings revealed that caffeine administration relative to the placebo condition resulted in heightened WM performance, but only for extraverted participants. We suggest based on previous theory and research that dopamine function (DA) may be the most plausible mechanism underlying this finding.