Physiology & behavior
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Physiology & behavior · Mar 2010
Randomized Controlled TrialConditioned effects of caffeine on performance in humans.
There is limited evidence for the conditioning of stimulant-like drug effects to previously-neutral stimuli in humans. Two studies tested whether the facilitatory effects of caffeine on cognitive performance can be conditioned to the context of drug administration. In Experiment 1, sixteen participants were divided equally into two groups: one group (the "paired" group) received 250 mg caffeine in a novel beverage prior to completing two computerized performance tests; the other group (the "unpaired" group) received the same beverage without caffeine (i.e. placebo) before testing. ⋯ After completing the conditioning sessions, tests for conditional responding were conducted by administering placebo in both contexts. During the conditioning phase, caffeine significantly improved reaction time performance relative to placebo, and this advantage was maintained at test in the CS+ context when placebo was administered in both contexts. Therefore the facilitatory effects of caffeine on performance can be elicited, in the absence of drug, by previously-neutral contextual stimuli that have been paired with drug administration.