The impacts of the processing levels on testing effect.

The testing effect refers to that retrieval practice enhances memory retention more than restudying does. A few previous studies have demonstrated that initial tests could improve memory by increasing recollection, and the depth of encoding could influence the degree of recollection and familiarity involved in retrieval process. The present study aimed to investigate whether the testing effect would be affected by the processing levels. Behavioral results revealed a significant testing effect in the shallow-processing condition, but not in the deep processing. Then, an event-related potential (ERP) experiment was conducted, showing that FN400 that represents familiarity occurred in the testing and restudying conditions with both processing levels, whereas the parietal old/new effect that indicates recollection only did not exist in the restudying with shallow-processing level. These findings revealed that the testing effect would be affected by the processing levels, and the underlying mechanism may be that tests could promote memory by enhancing recollection, which was involved in the deep rather than shallow-processing level during retrieval process. The practical meaning of the present study is that we can use tests to improve memory in a better and more efficient way.