Review
The critical role of retrieval practice in long-term retention

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Learning is usually thought to occur during episodes of studying, whereas retrieval of information on testing simply serves to assess what was learned. We review research that contradicts this traditional view by demonstrating that retrieval practice is actually a powerful mnemonic enhancer, often producing large gains in long-term retention relative to repeated studying. Retrieval practice is often effective even without feedback (i.e. giving the correct answer), but feedback enhances the benefits of testing. In addition, retrieval practice promotes the acquisition of knowledge that can be flexibly retrieved and transferred to different contexts. The power of retrieval practice in consolidating memories has important implications for both the study of memory and its application to educational practice.

Introduction

A curious peculiarity of our memory is that things are impressed better by active than by passive repetition. I mean that in learning (by heart, for example), when we almost know the piece, it pays better to wait and recollect by an effort within, than to look at the book again. If we recover the words the former way, we shall probably know them the next time; if in the latter way, we shall likely need the book once more.

William James [1]

Psychologists have often studied learning by alternating series of study and test trials. In other words, material is presented for study (S) and a test (T) is subsequently given to determine what was learned. After this procedure is repeated over numerous ST trials, performance (e.g. the number of items recalled) is plotted against trials to depict the rate of learning; the outcome is referred to as a learning curve and it is negatively accelerated and is fit by a power function. Thus, most learning occurs on early ST trials, and the amount of learning decreases with additional trials. The critical assumption is that learning occurs during the study phases of the ST ST ST… sequence, and the test phase is simply there to measure what has been learned during previous occasions of study. The test is usually considered a neutral event. For example, researchers in the 1960 s debated whether learning occurs gradually (e.g. through continual strengthening of memory traces) or in an all-or-none fashion, but they focused on study events as the locus of the effects and ignored the possibility that learning occurred during the retrieval tests 2, 3, 4, 5. Exactly the same assumption is built into our educational systems. Students are thought to learn via lectures, reading, highlighting, study groups, and so on; tests are given in the classroom to measure what has been learned from studying. Again, tests are considered assessments, gauging the knowledge that has been acquired without affecting it in any way.

In this article, we review evidence that turns this conventional wisdom on its head: retrieval practice (as occurs during testing) often produces greater learning and long-term retention than studying. We discuss research that elucidates the conditions under which retrieval practice is most effective, as well as evidence demonstrating that the mnemonic benefits of retrieval practice are transferrable to different contexts. We also describe current theories on the mechanisms underlying the beneficial effects of testing. Finally, we discuss educational implications of this research, arguing that more frequent retrieval practice in the classroom would increase long-term retention and transfer.

Section snippets

The testing effect and repeated retrieval

The finding that retrieval of information from memory produces better retention than restudying the same information for an equivalent amount of time has been termed the testing effect [6]. Although the phenomenon was first reported over 100 years ago [7], research on the testing effect has been sporadic at best until recently (but see Box 1 for some classic studies). In the last 10 years, much research has shown powerful mnemonic benefits of retrieval practice 8, 9, 10 . The data in Figure 1

Expanding retrieval schedules

The data in Figure 2 might be considered surprising in some quarters. For example, researchers who perform behavior analysis [27] or memory remediation among neuropsychological patient populations [28] believe that retrieval attempts should be arranged so that they do not produce errors (errorless retrieval is the watchword in these efforts). The fear is that if an error is produced than it will be learned, making learning of the correct responses more difficult. However, the data in Figure 2

Feedback enhances the testing effect

Although retrieval practice promotes superior long-term retention in the absence of feedback (Figure 1), providing the correct answer after a retrieval attempt increases the mnemonic benefits of testing 38, 39. Feedback that includes the correct answer increases learning because it enables test-takers to correct errors [40] and to maintain correct responses [41]. The critical mechanism in learning from tests is successful retrieval; however, if test-takers do not retrieve the correct response

Retrieval practice enhances transfer of learning

Are the mnemonic benefits of testing limited to the learning of a specific response? One criticism that could be leveled at research on the testing effect is that retrieval practice merely teaches people to produce a fixed response when given a particular retrieval cue, so the procedure simply amounts to drill and practice of a particular response. Thus, a key question is whether testing also promotes transfer of knowledge; that is, can the knowledge gained through testing be flexibly used to

Theories of the retrieval practice effects

Researchers have intensively studied the effects of retrieval practice and today we know much about conditions that produce the effect. However, theoretical understanding – or even proper theories of the effect – has lagged behind. One idea sometimes invoked to explain retrieval practice (testing) effects is that such practice simply permits re-exposure to material and causes overlearning of the set of material that can be retrieved 62, 63. Many experiments have discredited this hypothesis by

Educational implications

Retrieval practice produces greater long-term retention than studying alone. This finding suggests that testing, which is commonly conceptualized as an assessment tool, can be used as a learning tool as well [78]. In particular, practicing retrieval is beneficial when it requires effortful processing (e.g. production rather than recognition tests), it occurs multiple times with relatively long intervals between retrieval attempts, and it is followed by feedback after each attempt. Under these

Concluding remarks

The finding that retrieval practice yields substantial mnemonic benefits validates the quote from William James [1] at the outset: Students’ ‘active repetition’ via attempts to ‘recollect by an effort from within’ provides a much greater boost to retention than does ‘passive repetition’ from an outside source. The research we reviewed makes five points. First, retrieval practice often produces superior long-term retention relative to studying for an equivalent amount of time. Second, repeated

Acknowledgements

The authors are supported by a Collaborative Activity Grant from the James S. McDonnell Foundation and a grant from the Cognition and Student Learning Program of the Institute of Education Science in the U.S. Department of Education.

Glossary

Expanding retrieval schedule
testing of retention shortly after learning to make sure encoding is accurate, then waiting longer to retrieve again, then waiting still longer for a third retrieval and so on.
Feedback
providing information after a question. General (right or wrong) feedback is not very helpful if the correct answer is not provided. Correct answer feedback usually produces robust gains on a final criterion measure.
Negative suggestion effect
taking a test that provides subtly wrong

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