he physiological and behavioural effects of caffeine have been extensively researched. Adenosine receptor blockade is a principle action of caffeine resulting in a stimulant effect, e.g. concentration, energy, motivation to work. In a study by Lieberman et al. (1987), they found that caffeine had improved auditory vigilance tasks and visual reaction time performance; however, there were no significant effects of caffeine found on self-rated alertness. The vast majority of studies in this field have reported a number of beneficial psychological and performance effects of caffeine. Although some studies have been criticized for the use of caffeine doses that were in excess than those consumed in everyday life, when realistic doses were used, caffeine still reduces reaction times and improves attentional performance (Brice and Smith 2002).
             It is the wealth of research in this field that has attracted us to carry out the present study, to further investigate and determine the effects of caffeine on several measures of alertness and cognitive performance. With caffeine as the independent variable, and that alertness and cognitive performance as the dependent variables; we hypothesize that caffeine would have an effect on both alertness and cognitive performance. In addition, according to previous research, most of the studies had extensively investigated into the effects of caffeine on performance based on psychomotor speed and reaction times as well as mood, but very few had mentioned much on its effects on short-term memory. Therefore, in the present study, we have chosen to inves
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