Recalling more each time: context change effects in hypermnesia.

Hypermnesia, the increase in recall over trials without relearning or re-exposure to the studied items, has intrigued researchers since Ballard first reported the effect in 1913. In the typical hypermnesia study, additional retrieval trials are unexpected, and when announced, may induce context changes that re-focuses attention and effort on retrieving unrecalled items. The present studies examined the effects of context change on retrieval by telling some participants prior to study (trials-known condition) that three trials will be given to recall line drawings (Experiment 1) or words (Experiment 2) whereas others were not so informed (hypermnesia condition). Results of Experiment 1 revealed hypermnesia but no between-group differences on the sub-processes of item gains, losses, or intrusions. In Experiment 2, hypermnesia and between-group differences were found for item gains and intrusions, results that were marginally significant when data were aggregated across both experiments. Results are discussed in terms of the change in cue set hypothesis (Raaijmakers & Shiffrin, 1980) and the effects of internal and external context changes on hypermnesia. Suggestions for future studies are also presented.