The influence of caffeine on working memory and salivary habituation to food cues

It is well-established that both physiological and operant responses to food cues habituate, or decrease, after repeated exposure. An increased rate of habituation to food cues has been found decrease subsequent energy intake. Habituation rate is also associated with attention and working memory. Evidence suggests that caffeine may improve working memory through its interaction with dopamine. The purpose of this study was to test the hypothesis that caffeine would increase the rate of habituation by improving working memory. Male and female (n=60) non-obese adults (BMI < 30) received caffeine (2mg/kg) or placebo in a double blind, crossover study. Participants then completed n-back and digit span working memory tasks followed by 11 consecutive salivation trials with pizza (trials 1-8) and brownies (trials 9-11). Between each salivation trial, participants were randomized to either a high or low memory workload task or no task. Throughout the study measures of hunger, thirst liking, and desire to eat were recorded along with ad libitum energy intake. We found salivary habituation across trials 1-8, however there was no effect of caffeine or workload on the rate of habituation. Caffeine did not influence accuracy or reaction time on working memory tasks. In males only caffeine decreased intake of energy from pizza, but not brownies. These findings suggest that caffeine does not influence the rate of habituation or performance in these working memory tasks, although caffeine may have a small effect on energy intake.