The two processes underlying the testing effect- Evidence from Event-Related Potentials (ERPs)

Theoretical explanations of the testing effect (why people learn better from a test than a re-study) have largely focused on either the benefit of attempting to retrieve the answer or on the benefit of re-encoding the queried information after a successful retrieval. While a less parsimonious account, prior neuroimaging evidence has led us to postulate that both of these processes contribute to the benefit of testing over re-study. To provide further empirical support for our position, we recorded ERPs while subjects attempted to recall the second word of a pair when cued with the first. These ERPs were analyzed based on the current response accuracy and as a function of accuracy on the subsequent test, yielding three groups: the first and second tests were correct, the first was correct and the second was not, both were incorrect. Mean amplitude waveforms during the first test showed different patterns depending on the outcome patterns: Between 400 and 700 ms the amplitudes were most positive when both tests were correct and least positive when both were incorrect; mean amplitudes between 700 and 1000 ms only differed as a function of subsequent memory. They were more positive when the second test was correct. Importantly, the later component only predicted subsequent memory when the answers were not overlearned, i.e. only correctly recalled once previously. We interpret the 400-700 ms time window as a component reflecting a retrieval attempt process, which differs as a function of both current and subsequent accuracy, and the later time window as a component reflecting a re-encoding process, which only involves learning from tests, both of which are involved in the testing effect.