My friend Wim van den Broeck shared this study by Highgam et al. with me. In this study, the researchers tried to determine the effectiveness of spaced restudying in promoting durable learning and to compare it to the efficacy of spaced retrieval practice. The participants had to learn Swahili–English translation pairs in the online experiments. But the researchers also wanted to know something more:

…students may attempt to engage in retrieval practice in a setting where they must be silent (e.g., covertly retrieving answers to an instructor’s questions in a classroom setting or using flashcards in a library). Additionally, some smartphone apps designed to facilitate learning through retrieval practice (e.g., RememberMore and MosaLingua) do not require users to make overt responses, only to think of them. Also, apps such as Anki allow users to create their own flashcards or download sets from others. With these apps, users simply indicate when they want to see the flashcard again by selecting a particular option (e.g., Again, Hard, Good, and Easy), with each option determining when to show the card again. Therefore, it is important to establish whether these students will reap the benefits of retrieval practice to the same extent as students who are retrieving information in a setting where overt production is more likely.

So, what did the researchers learn?

Response format had no effect on recall, but surprisingly, final test performance for restudied items exceeded both the overt and covert retrieval conditions. In Experiment 2, we manipulated the requirement to make a memory rating. If a memory rating was required, final test restudy performance exceeded retrieval performance, replicating Experiment 1. However, the pattern was descriptively reversed if no rating was required. In Experiment 3, the memory rating was removed altogether, and we examined recall performance for items restudied versus retrieved once, twice, or thrice. Performance improved with practice, and retrieval performance exceeded restudy performance in all conditions.

It seems that this study delivers more questions than answers. The Learning Scientists tried to answer these questions:

Clearly, the effect has to do with the metacognition happening when participants are asked to predict how much they will remember, on each item, with an opportunity to restudy. There are other studies that ask participants how much they will remember later on (2), but these are global estimates and not quite the same thing as what we’re seeing here, where the estimates are happening during study. One suggestion made by the researchers is that this could be due to something called the “changed-goal hypothesis”. This means that the participants might have received those ratings and changed their strategy such that they were hyper-focused on retaining the restudied items and put less effort into the retrieved items (possibly because they were metacognitively aware that they were getting them wrong!).

Abstract of the study:

We investigated spaced retrieval and restudying in 3 preregistered, online experiments. In all experiments, participants studied 40 Swahili–English word pair translations during an initial study phase, restudied intact pairs or attempted to retrieve the English words to Swahili cues twice in three spaced practice sessions, and then completed a final cued-recall test. All 5 sessions were separated by 2 days. In Experiment 1, we manipulated the response format during retrieval (covert vs. overt) and the test list structure (blocked vs. intermixed covert/overt retrieval trials). A memory rating was required on all trials (retrieval: “Was your answer correct?”; restudy: “Would you have remembered the correct translation?”). Response format had no effect on recall, but surprisingly, final test performance for restudied items exceeded both the overt and covert retrieval conditions. In Experiment 2, we manipulated the requirement to make a memory rating. If a memory rating was required, final test restudy performance exceeded retrieval performance, replicating Experiment 1. However, the pattern was descriptively reversed if no rating was required. In Experiment 3, the memory rating was removed altogether, and we examined recall performance for items restudied versus retrieved once, twice, or thrice. Performance improved with practice, and retrieval performance exceeded restudy performance in all conditions. The reversal of the typical retrieval practice effect observed in Experiments 1 and 2 is discussed in terms of theories of reactivity of memory judgments.