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Twelve male students who normally ate a large lunch and 12 who normally ate only a light lunch performed a sustained attention task before and after eating a light lunch and before and after eating a heavy lunch. The speed and accuracy of performance were measured; so also were temperature, pulse rate and subjective estimates of tension, alertness and hunger. The changes brought about by the meals were examined. Speed alone showed no change over the lunch interval. Of the remaining seven measures, only temperature, which seems to reflect endogenous processes, was unaffected by the size of the lunch that was eaten. Accuracy, pulse rate and hunger were influenced by the size of the habitual lunch as well as by the size of the experimental lunch. Tension and alertness were responsive only to the size of the experimental lunch. The results are discussed in relation to diurnal rhythms, with a particular emphasis on the acquisition of endogenous component processes, as exemplified by habits of eating. [ABSTRACT FROM AUTHOR]

Forty students performed on a perceptual discrimination task both before and after a mid-day lunch interval. Half of the students consumed a three-course lunch during the interval, the remaining half abstained from lunch. It was found that the actual ability to discriminate between events was significantly impaired following the consumption of lunch, but did not alter when no food was ingested. The magnitude of the post-lunch dip in discrimination efficiency was significantly greater in the less 'neurotic' and the more 'extraverted' individuals, according to scores on the Eysenck Personality Inventory, and was also significantly though negatively related to the extent of the drop in sublingual temperature that occurred over the lunch interval. It is concluded that operational efficiency and safety may be at risk following lunch. [ABSTRACT FROM AUTHOR]