The critical importance of timing of retrieval practice for the fate of nonretrieved memories.

Retrieval practice performed shortly upon the encoding of information benefits recall of the retrieved information but causes forgetting of nonretrieved information. Here, we show that the forgetting effect on the nonretrieved information can quickly evolve into recall enhancement when retrieval practice is delayed. During a time window of twenty minutes upon the encoding of information, the forgetting effect observed shortly after encoding first disappeared and then turned into recall enhancement when the temporal lag between encoding and retrieval practice was prolonged. Strikingly, recall enhancement continued to emerge when retrieval practice was postponed up to one week. The results illustrate a fast transition from the forgetting of nonretrieved information to recall enhancement. This fast transition is of relevance for daily life, in which retrieval is often selective and delayed.

The Effects of Interspersed Retrieval Practice in Multiple-List Learning on Initially Studied Material.

The forward testing effect (FTE) refers to the finding that retrieval practice of previously studied material can facilitate retention of newly studied material more than does restudy of the material. The goal of the present study was to examine how such retrieval practice affects initially studied, unpracticed material. To this end, we used two commonly applied versions of the FTE task, consisting of either three (Experiment 1) or five (Experiment 2) study lists. While study of list 1 was always followed by an unrelated distractor activity, study of list 2 (3-list version) or lists 2, 3, and 4 (5-list version) was followed by either interim restudy or retrieval practice of the immediately preceding list. After studying all lists, participants were either asked to recall the first or last study list. Results showed that, for both the three-list and five-list versions, interim retrieval practice led to a typical FTE, irrespective of whether unrelated or categorized study lists were used. Going beyond the prior work, interim retrieval practice was found to have no effect on initially studied, unpracticed material, regardless of the type of study material. The findings suggest that using interim retrieval practice as a study method can improve recall of the last studied list without incurring a cost for the initially studied material. Our results are difficult to align with the view that retrieval practice induces context change, but are consistent with the idea that retrieval practice can lead participants to employ superior encoding strategies.