Abstract

EFFECTS OF CAFFEINE IN THE AFTERNOON UPON THE ENCODING OF NEW INFORMATION AND LAPSES OF ATTENTION

Andrew P. Smith*, PhD

ABSTRACT

Background: The behavioural effects of caffeine have been widely studied, and most studies have administered caffeine in the morning. The present study examined the effects of caffeine given in the post-lunch period. Caffeine increases the speed of encoding new information even when the person is alert, whereas it reduces lapses of attention when the person is fatigued. This was examined in the present study. Methods: Ninety-six university students took part in the study. There were twenty-four in each of the groups formed by combining lunch/no lunch conditions and caffeine/placebo. The caffeine manipulation was double-blind, and 100mg of caffeine was added to decaffeinated coffee in the caffeine conditions. Participants carried out a baseline test session in the morning, followed by the lunch and drinks conditions. There was then a post-drink test session one hour later. The test battery included measures of cardiovascular function, the speed of encoding new information, lapses of attention and indices of selective attention. Results: Consumption of lunch led to a higher pulse rate than when no lunch was consumed, but caffeine had no significant effect on cardiovascular parameters. Caffeine consumption led to faster encoding of new information at the start of the test session and reduced lapses of attention at the end of the session. There were no significant effects of caffeine on measures of selective attention. Conclusion: Administration of caffeine after lunch showed the predicted profile of behavioural change, and this was observed whether lunch was consumed or not. Lunch led to a higher pulse rate, whereas caffeine had no significant effect on cardiovascular outcomes.

Keywords: Caffeine, Afternoon, Post-lunch, Encoding, Lapses of attention, Categoric Search, Selective attention, Blood pressure, Heart rate.