The Effect of Memory Load on the Circadian Variation in Performance Efficiency Under a Rapidly Rotating Shift System*

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Abstract
Experimental shift work studios have typically found body temperature and performance efficiency to show very similar circadian rhythms. However, the performance tasks used have placed little, if any, reliance on short term memory. Studies of the variation in performance during the normal waking day have found performance on most tasks to improve over the day but that on short term memory tasks to decrease. The present paper reports an experimental study of the performance of two subjects on a rapidly rotating (-2-2) shift system. Three versions of a now performance test, each with a different memory load, wore administered four times per shift. With the low memory load version, performance showed a high positive correlation with body temperature and was poor during the night shift. However, with the high memory load version, performance was negatively correlated with temperature and was best during the night shift. It is concluded that future shift work studies must take into account the memory load of the task under investigation.