CAFFEINE, BREAKFAST CEREAL AND TIME OF DAY: EFFECTS ON ALERTNESS, ENCODING AND RECALL

Andrew P. Smith PhD*

ABSTRACT

Background: There is considerable literature on the effects of caffeine on cognition and alertness. However, there is no consensus on sensitive measures that can be used as positive controls in the studies of the effects of other changes in state. The present study examined whether encoding of new information and ratings of alertness after a cognitive test battery are indicators which demonstrate the effects of caffeine in different contexts. The changes in state investigated here were those observed after consumption of breakfast cereal. Previous research has identified sensitive tests, namely free recall of a list of words and pre-test alertness, that are reliably observed when breakfast cereal is consumed in the early morning. Methods: The present research examined contextual factors that may be important in these breakfast effects. The first study examined the effects of breakfast at lunchtime and the second examined the possible role of sleep inertia by studying night workers who had a sleep in the day and then had breakfast before starting their shift. Results: The results showed that caffeine led to faster encoding of information in both studies and also increased alertness after the performance tests. In contrast, there were no effects of consumption of breakfast cereal on the free recall task, although alertness before the test battery was increased following the consumption of cereal in both studies. Conclusion: These results demonstrate that caffeine can be used as a positive control when the sensitive tasks used in this study are included. The effects of breakfast cereal on memory observed in the early morning are not due to consuming breakfast per se nor to sleep inertia. Further research involving a longer fasting period is now needed to determine whether this is the crucial factor leading to cereal improving recall. The effect of cereal on pre-test alertness shows that there are reliable effects which may be due to eating per se rather than post-digestive changes in state.

Keywords: Caffeine; Breakfast Cereal; Encoding; Alertness; Free recall.