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Caffeine (a methylxanthine) is a central nervous system stimulant (Nehlig, Daval, and Debt)', 1992). It is the most commonly consumed psychotropic drug (e.g., Gilbert,1984) and possesses a limited tendency to generate physical dependence (Griffiths and Woodson, 1988). Low doses often generate positive mood states and potential improvements in performance. High doses may (cf., Griffith and Woodson, 1988) or may not (Mathew and Wilson, 1990) generate unpleasant moods or anxious feelings in individuals who tend to suffer from anxiety. During the last decade, an increasing number of scientists have reported various effects of caffeine treatment or deprivation on physiological (e.g., cardiovascular) functioning, health and illness (Brown, Bolton- Smith, Woodward and Tunstall-Pedoe, 1993), and behavior (e.g., mood or performance).