The influence of repeated study and repeated testing on the testing effect and the transfer effect over time.

Many studies have shown that compared to the restudy condition (RS), retrieval practice (RP) enhances the long-retention memory of retrieved items (i.e., the testing effect), and facilitates later memory of non-retrieved but related items (i.e., the transfer effect). However, previous studies have usually used repeated study and repeated testing, which are included in study-testing cycles. Therefore, it is unclear to what extent the factors of repeated study and repeated testing influence testing and transfer effects over time. In this study, participants studied sentences that described various episodes, then tested a half subset of the original sentences under three conditions (RP, RS, control). After retention intervals of 10 min, 1 day and 7 days, they recalled all of the information in the sentences. The results showed that the testing effect was enhanced by repeated study or repeated testing, while the transfer effect occurred only after both repeated study and repeated testing. Furthermore, repeated study or repeated testing slowed down the forgetting of retrieved items, while the forgetting of non-retrieved items occurred after both repeated study and repeated testing. The testing effect increased over time, but the transfer effect remained relatively stable over time. These results clarified different roles of multiple study repetitions and testing opportunities in the testing effect and the transfer effect, and suggest that the repeated retrieval could be combined with repeated study to optimally promote long-term retention of the memory of tested and non-tested items.