Why rereading can feel more useful than it is

A worked solution looks straightforward when every line is on the page. The substitution seems obvious, the algebra follows, and the answer is there to confirm that everything makes sense. Close the book, however, and it may be difficult to decide which equation to write first. The page was doing part of the work.

That gap between following an explanation and producing one is easy to miss. Rereading gives you information while you judge how well you know it. In an exam, a conversation or a new problem, the same information may be absent. Research on judgments of learning shows how this difference can make predictions about future recall too optimistic. ¹

When the answer is already in view

Asher Koriat and Robert Bjork examined this problem in a 2005 study using pairs of words. Seeing a cue and its answer together could make the association seem more useful than it would be when the cue appeared alone. Participants had to estimate a future situation while looking at information that would be missing from that situation. Word pairs are simpler than a textbook chapter, but the study identifies a useful distinction: seeing an answer can make it easier to overestimate how readily that answer will come to mind later. ¹

Consider learning that a pressure difference drives the movement of a fluid. With the explanation open, the causal connection may be easy to follow. Asked later why water moves through a particular pipe, you have to identify the relevant idea yourself. Being able to recognise the explanation and being able to retrieve it are different demands. A study session can make progress on one without showing how much progress has been made on the other.

What happened a week later

Henry Roediger and Jeffrey Karpicke tested students who learned short prose passages in experiments published in 2006. Some students spent additional opportunities studying the material. Others used those opportunities to write down what they could remember, without seeing the passage. The researchers then assessed retention after different delays. ²

The result depended on when they tested it. After five minutes, repeated study could produce better recall than repeated testing. After two days or a week, the earlier recall attempts produced better retention. Repeated studying also left students more confident about how much they would remember. The immediate feeling of success did not reliably identify the method with the better delayed result. ²

This is why an evening of fluent reading can be hard to evaluate. A student may finish with more information immediately available, yet still need practice producing it after a delay. Every group first had something to read. The comparison concerned how students used their further study opportunities, once the material had already been introduced. ²

Recall can involve understanding

Retrieval practice is sometimes described as if it only means memorising definitions. In a 2011 study, Karpicke and Janell Blunt compared studying science texts through repeated recall with studying through concept maps. A week later, the retrieval group performed better on questions about stated information and on questions requiring connections between ideas. The researchers also compared different final test formats. ³

The result concerns particular science texts and learning tasks. Concept maps can still be used to organise ideas; here, however, retrieving the text contributed more to the conceptual knowledge assessed a week later. The choice of question matters. Recalling the definition of acceleration is a different exercise from explaining how an object can accelerate while its speed stays constant. Both involve memory, but the second also requires the relationship between velocity, direction and acceleration. ³

Checking the answer matters too

A recall attempt gives you something concrete to inspect. You might have remembered the result but omitted a condition, confused two terms or arrived at the correct answer through a faulty argument. Comparing the attempt with a reliable explanation makes these differences visible. In a maths problem, an answer alone may leave them hidden.

Feedback research also complicates the assumption that only wrong answers need attention. In two experiments reported by Andrew Butler, Karpicke and Roediger in 2008, feedback improved later retention of initially correct answers made with low confidence, as well as helping correct errors. The tasks involved general-knowledge multiple-choice questions followed by cued recall. The finding gives a reason to examine uncertain answers even when they happen to be right, rather than treating the correct mark as the end of the matter. ⁴

Why the interval between sessions matters

A separate question is when to return to the material. Nicholas Cepeda and colleagues varied the gap between learning and review in a 2008 study of more than 1,350 adults learning facts. The final test came after a further delay. For each test delay, performance first improved as the study gap increased and then worsened when the gap became too long. The more distant the final test, the longer the estimated best study gap tended to be. ⁵

There was no single interval that was best regardless of the deadline. Nor was this a trial of an entire school course: participants learned short factual answers under controlled conditions. It gives evidence for spreading encounters with material over time, while leaving substantial decisions about real coursework unresolved. A student returning to yesterday’s topic and another revising for an exam months away should not assume that the same spacing rule must suit both. ⁵

Where rereading still belongs

An explanation that was confusing the first time may need another reading, a different example or help from a teacher. After an unsuccessful attempt, returning to the relevant passage can address the exact gap that caused the difficulty. The practical issue is how to tell whether that return helped. A later explanation or problem attempt, made without the answer in view, provides evidence that another comfortable reading cannot supply on its own. That later attempt gives you a clearer basis for deciding what to study next than the number of times the page has been read.