Time of day and level of processing

The time of day at which material is presented has a differential effect on immediate and delayed retention. It has been suggested that this may be mediated by a shift in the type or level of processing that subjects spontaneously engage in. Three experiments are described that were designed to test this suggestion. Experiment 1 found the acoustic similarity effect on short-term memory to be greater at 1000 h than at 1900 h. Experiment 2 showed the semantic similarity effect on long-term memory to be greater at 1930 h than at 1030 h. Experiment 3 demonstrated that interposing a short-term memory task between the presentation of a list of words and its subsequent recall had a greater detrimental effect on list learning at 1030 h than at 1930 h. It is suggested that, if free to do so, subjects may spontaneously place more reliance on maintenance processing in the morning, but more on elaborative processing in the evening.