Caffeine is the most widely consumed and socially-acceptable of psychoactive drugs. Its arousing properties, both physical and behavioural, have been studied for almost a century, but interest in its effects on cognition is recent. The first tasks employed in cognitive studies were chosen without regard to underlying theory: interpretation of the outcomes therefore remained atheoretical. Four theoretically-based hypotheses, tapping different aspects of cognitive function were, therefore, tested under caffeine at 0, 2 and 4 mg/kg body weight. The paradigms were as follows: a simple information-processing task at two levels of difficulty; the free recall of spoken word lists; a numeric version of the Stroop task; and a lateralized version of the Posner task. A main effect of caffeine was found in the Stroop task where the highest dose caused a significant disruption of response over and above that due to the Stroop effect per se. No other main effects were found, but interactions with the variables of introversion-extraversion and sex were implicated as potent and confounding factors in the effect of caffeine on cognition. An interaction of stimulus type and receptive hemisphere in the Posner task showed that caffeine is able to reverse the normal locus of hemispheric processing: the right hemisphere became more efficient for sequential inputs and the left hemisphere for holistically-analyzed stimuli. It is suggested that a central action of caffeine is to increase stimulus sampling rates, and that its effects on both general arousal and specific information-processing functions follow from this. The general implication of the findings is that the cognitive effects of caffeine are real but subtle, resting on very specific conjunctions of variables, and would thus be more readily demonstrated in uniform groups of individuals, under precisely defined conditions of testing.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:696388 |
| Date | January 1997 |
| Creators | Barraclough, Mary Susan |
| Publisher | University of Leicester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/2381/31294 |
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