TIME OF DAY AND NATURALISTIC PROSPECTIVE MEMORY

Fatigue and circadian rhythms have been proposed as explanations of ti me-of-day effects on retrospective memory. Both explanations predict p oor morning performance, a midday performance peak, and then declining performance and poorest recall in the evening. Whereas this pattern h as been found in research on retrospective memory using ordered serial recall, in the single relevant study on prospective memory, performan ce was found to be highest in early morning, followed by a midday decl ine with no additional declines. Using post hoc analyses, we investiga ted older adults' prospective memory throughout the day. Data were tak en from two studies we had conducted previously and one recently compl eted experiment. In each of the three experiments, we examined simulat ed medication and appointment adherence over a 13-day period and found prospective memory to be better in the morning than at midday. In two experiments, we found no further decline after midday, and iii the th ird experiment, performance actually increased in the evening compared with midday. These post hoc analyses provide preliminary evidence tha t factors different from or at least in addition to fatigue and circad ian rhythms produce time-of-day effects on prospective memory, indicat ing the need for more programmatic research in the future. One explana tion for these findings is that attentional capacity devoted to prospe ctive-memory task varies inversely as a function of activity level dur ing different times of the day.