Why rereading your notes is not enough

When you reread your notes, everything feels familiar. The words, the diagrams, the order of the ideas, you recognize all of it. That recognition gives you the sense that the information is well settled in your memory. But recognizing a page while it is in front of you and retrieving its content on exam day are two different tasks.

A survey of 177 students found that most of them reread their notes or textbook, and relatively few quiz themselves. The authors speak of an illusion of competence (Karpicke et al., 2009). In the review by Dunlosky and colleagues, rereading is among the low utility techniques, next to highlighting and summarizing (Dunlosky et al., 2013). In other words, the most common method is also one of those with the thinnest evidence. In high school as in college, many people spend their evenings on this technique, because it is easy and reassuring.

In experiment 2 by Roediger and Karpicke, 120 students learned prose texts. Some read once and then quizzed themselves three times. Others reread the text four times. A week later, the first group remembered 61% of the ideas and the second 40% (Roediger and Karpicke, 2006).

One detail matters a lot. At 5 minutes, rereading gave a better score. Between that quick test and the one a week later, the rereaders forgot 52% of what they knew, against 14% for those who quizzed themselves (Roediger and Karpicke, 2006). If you test yourself right after rereading, it will therefore feel like it works. The forgetting comes afterwards. It is the same mechanism as when everything feels learned on Sunday night before a quiz and everything has vanished by Wednesday. The key point is that when you test changes the conclusion you draw about your method.

In the study, the students who reread were the most confident they would remember, and they are the ones who forgot the most (Roediger and Karpicke, 2006). This is not an isolated case. With Swahili vocabulary, the students’ predictions of their own success were not related to how well they actually did (Karpicke and Roediger, 2008). In other words, your feeling of mastery is not a good measuring instrument.

Bjork, Dunlosky and Kornell describe these mistaken beliefs of students and suggest replacing them with desirable difficulties, study situations that are a bit more demanding but longer lasting (Bjork et al., 2013). The trap of rereading is precisely that it is comfortable. If your study session never puts you in difficulty, ask yourself whether you retrieve anything or just recognize. A simple test is to close your notes, write down what you remember, and then compare.

You do not need to stop rereading. Reread once to understand, then move on to quizzing. Close your notes, answer questions, correct yourself, and start again a few days later. In the experiments, reading once then quizzing three times beat four rereadings (Roediger and Karpicke, 2006). For the details of the method, see Active recall, why quizzing yourself beats rereading.

For spacing, keep the example calculated from the study by Cepeda and colleagues. With an exam in 10 days, review the material 2 to 4 days after the first session (Cepeda et al., 2008). And to see where this fits, the page How to study effectively, according to the research compares the ten techniques. In high school, that means redoing the course questions for your history chapter with the notebook closed, instead of rereading the review sheet a fifth time the night before the test.