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The aim of the present study was to examine the effects of breakfast and caffeine on performance, mood and cardiovascular functioning in the late morning and after lunch. Forty-eight subjects were tested at 07.45 and subjects then assigned to one of the four conditions formed by combining caffeine and breakfast conditions. Subjects in the caffeine condition were given a dose of 4 mg/kg, the caffeine manipulation being double blind. At 11.15 subjects were given another coffee (subjects remained in the same caffeine condition) and had lunch at 12.30. Performance was examined prior to lunch (11.30) and after lunch (14.00). Effects of breakfast on recognition memory (lower false alarm rate) and logical reasoning (reduced accuracy) were found in the late morning but not after lunch. However, a semantic processing task was performed more slowly by the breakfast group after lunch. Caffeine improved performance on a sustained attention task, the logical reasoning task and semantic memory task. Subjects given caffeine also reported greater alertness and feelings of well-being, whereas the effects of breakfast on mood changed from the late morning to early afternoon. Few interactions between breakfast and caffeine conditions were obtained.

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) on human performance and mood. However, these factors have usually been considered in isolation, which is not representative of what happens in real life. There have, however, been a few studies which have looked at the interactions between them. For example, Smith et al. (1990) examined the effects of caffeine on the post-lunch dip in sustained attention and showed that caffeine removed the post-lunch impairment. Millar et al. (1992) have demonstrated that consumption of lunch can reduce the negative effect of alcohol observed in some aspects of performance. In contrast to this, previous research (e.g. Oborne & Rogers, 1983) suggests that caffeine does not remove the detrimental effects of alcohol.The main aim of the present study was to examine the separate and combined effects of caffeine, lunch and alcohol to provide further insight into their modes of action and to allow comparison of the magnitude of the effects of the different factors. Previous research has also shown that there are individual differences in the effects of caffeine, alcohol and lunch. In the case of caffeine it appears to be impulsivity which predicts the size of the effect. In contrast to this, anxious subjects tend to show a smaller post-lunch dip than non-anxious subjects. There are also individual differences in the effects of alcohol, with extravert, anxious subjects showing the greatest impairments after alcohol. These personality effects were examined in the present study but the findings are not reported here. METHODS