Retrieval from semantic memory at different times of day.

This study is concerned with retrieval from semantic memory at different times of day. Three groups of eight subjects classified high-, medium-, and low-dominance category members as positive or negative instances of specified test categories in the morning (09.00), afternoon (14.00), or evening (20.00). Classification latencies became faster over the day. Positive test instances were classified faster than negative test instances. There was an interaction such that the difference in the time taken to classify high- relative to low-dominance category members was greater for positive instances and smaller for negative instances in the morning compared with the afternoon and evening. We propose that retrieval efficiency is lower and that a different retrieval strategy is adopted in the morning compared with later in the day. We suggest that the retrieval strategy adopted in the morning serves to minimize cognitive load and effort in a state of relatively low circadian arousal.