PMC

Average self-reported mood scores pre- and postcapsule administration. Mood scores were higher in the normal state than in the abstained state, and caffeine increased mood in the abstained state only. Mood decreased following placebo in the normal state (paired t test pre- to postcapsule: *p<0.01). Bars are SEM

Average reaction times for the choice reaction time task after caffeine and placebo in the abstained and normal state. Caffeine decreased reaction times in the abstained state (paired t test placebo to caffeine: *p<0.01), but not in the normal state. Bars are SEM

Average accuracy (percent correct responses) for the 1-back and 2-back task conditions in the memory task following placebo and caffeine in the abstained (AP and AC, respectively) and normal state (NP and NC, respectively). Caffeine increased accuracy in the 1-back task (paired t test AP to AC: *p<0.05), but did not significantly affect accuracy in the 2-back task. Bars are SEM

Average reaction times for the congruent and incongruent task conditions in the flanker selective attention task following placebo and caffeine in the abstained (AP and AC, respectively) and normal state (NP and NC, respectively). Caffeine decreased reaction time in the incongruent task (paired t test AP to AC and NP to NC: *p<0.05), but not in the congruent task. Bars are SEM