Abstract

FURTHER INVESTIGATION OF THE EFFECTS OF CAFFEINE ON IMPLICIT MEMORY, ALLOCATION OF MEMORY RESOURCES, SEMANTIC MEMORY AND EXECUTIVE FUNCTION

*Dominic P. Nguyen-Van-Tam, PhD and Andrew P. Smith, PhD

ABSTRACT

Background: Research has shown that the performance of semantic processing and logical reasoning tasks improves after caffeine. There is also some evidence that implicit memory and allocation of memory resources are improved by caffeine. The aims of the present study were twofold; firstly, to attempt to replicate the effects of caffeine on implicit memory and allocation of memory resources and secondly, to investigate whether the effects of caffeine on semantic memory and executive function were mediated by the speed of reading and encoding of lexical information. Methods: Participants (University students, N=56) completed a laboratory session in the morning or afternoon. Separate groups either received caffeine or a placebo. The caffeine dose was 4mg/kg and was carried out double-blind. Tasks measuring semantic processing, logical reasoning, implicit memory and allocation of memory resources were used. Results: The performance of the semantic processing and logical reasoning tasks was significantly better in the caffeine condition. These effects did not reflect the speed of encoding of the information. Previous findings on the effects of caffeine on implicit memory and allocation of memory resources were not replicated. Conclusion: The results from this study confirm the effects of caffeine on semantic processing and executive function. These effects did not reflect the speed of encoding the new information. In contrast, no reliable effects of caffeine on implicit memory and allocation of memory resources were found. These results confirm that semantic processing and logical reasoning tasks are good indicators of the beneficial effects of caffeine, whereas other aspects of memory show little effect.

Keywords: Caffeine; Semantic processing; Executive function; Logical reasoning; Implicit memory; Allocation of memory resources.