Flavour liking and preference conditioned by caffeine in humans.

When caffeine consumers repeatedly experience a novel flavoured drink containing caffeine, the rated pleasantness of the drink flavour increases progressively. These results could be interpreted in terms of the flavour acting as a Pavlovian conditioned stimulus (CS) predicting the consequences of caffeine ingestion. However, all studies of this phenomenon to date have used between-subjects designs, and one criticism of this is that changes in pleasantness might have arisen from nonspecific effects.

How habitual caffeine consumption and dose influence flavour preference conditioning with caffeine.

This study investigated the effects of both habitual caffeine use and dose administered in determining the ability of caffeine to reinforce conditioned changes in flavour preference. Thirty overnight-withdrawn moderate caffeine consumers and 30 non or low-dose caffeine (non/low) consumers evaluated five novel-flavoured fruit teas. Subsequently, their median-rated tea was used in four ensuing conditioning sessions.

Impairments in working memory associated with naturalistic dieting in women: no relationship between task performance and urinary 5-HIAA levels.

The present study investigated the question of whether the previously observed impairments of working memory characteristic of dieting to lose weight can be explained in terms of preoccupying cognitions relating to body shape or to alterations in serotonergic function resulting from a low dietary intake of tryptophan. The population comprised female non-dieting, lower restrained eaters (N=23), non-dieting higher restrained eaters (N=11) and current dieters (N=19). Each participant completed three tasks, each of which selectively loaded on to a different sub-component of working memory.

Caffeine reinforces flavour preference in caffeine-dependent, but not long-term withdrawn, caffeine consumers.

Rationale: Previous studies have shown that caffeine can reinforce flavour liking in overnight deprived moderate caffeine consumers (e.g. average of 250 mg/day) but not in low consumers (<120 mg/day).

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.