Effect of caffeine-deprivation on liking for a non-caffeinated drink

Liking for a novel non-caffeinated drink decreases when regular caffeine consumers are exposed repeatedly to that drink when caffeine-deprived; however, this dislike is not manifest if people are subsequently tested when not caffeine-deprived (Yeomans et al., 2000a). The present study investigated the basis for this effect, and in particular, whether the decrease in liking observed is specific to the drink flavour experienced during caffeine-deprivation. Twenty-four caffeine consumers evaluated five novel drinks (fruit teas) at pre-training. For each person, the drink with the median liking score was subsequently consumed mid-morning after 12 h caffeine-deprivation on four non-consecutive training days. Rated pleasantness of this drink decreased significantly over these four training days. Subjects subsequently re-evaluated all five drinks on a test day when half the consumers were given 100mg caffeine two hours prior to testing, with the remainder receiving placebo. The group who remained deprived continued to express depressed liking for the exposed (target) drink, compared to their pre-training rating of that drink. In contrast, rated pleasantness was not depressed compared to pre-training ratings in the group who had received caffeine prior to testing. Rated pleasantness of the four unexposed drinks was equivalent to pre-training ratings, for both groups, suggesting that the effect of exposure on ratings of the target drink was specific to that drink. As expected, there was some evidence of improved mood in the group receiving caffeine on the test day; but as it was only ratings of the target drink that differed across groups, the group difference cannot be attributed to general effects of mood on use of the rating scale. These data suggest that the reversal of acquired changes in liking for drinks when consumers are changed from a caffeine-deprived to an undeprived condition is best explained in terms of state-dependent learning, that is specific to the drink experienced during caffeine-deprivation.