The long and the short of it? An explanation of the spacing effect over long time scales

Abstract

The spacing effect is the observation that repetitions spaced out in time produce better learning and retention than repetitions massed closer together in time. There has been a long history of research on the spacing effect but there is not currently a satisfactory explanation for why it occurs. Furthermore, while empirical data on the spacing effect across long timescales has been accumulating, this data has not been integrated into the theoretical explanations of the effect. In this thesis I explore a new theory of why the spacing effect occurs, one based on memory reconsolidation. In experiments 1 to 3, I test paradigms for their suitability for testing a prediction of the reconsolidation account of the spacing effect. Unfortunately, the findings from previous studies did not replicate, making it impossible to probe the reconsolidation account of the spacing effect using these paradigms. In Experiment 4a I found a suitable paradigm and in Experiment 4b I set about testing a prediction of the reconsolidation account. Specifically, that manipulating the strength of a memory should influence the reconsolidation process and, as a consequence, the spacing effect. The results of experiment 4b were consistent with this prediction. In Experiments 5a and 5b I tested a second prediction of the reconsolidation account of the spacing effect. Specifically, that different mechanisms underly the spacing effect over short and long timescales. Consistent with the reconsolidation account of the spacing effect it appears retrieval difficulty influences the spacing effect over short timescales but not long timescales. I conclude by exploring future experiments that should be conducted in order to further test the reconsolidation account and the functional significance of the spacing effect.