In the paper, Carpenter and her coauthors describe spacing as a strategy to learn in small doses over time. It’s the opposite of cramming the night before an exam

Carpenter says there isn’t a universal rule about how much time to schedule between practice sessions. But research shows returning to the material after forgetting some—but not all—of the content is effective.

Retrieval practice is a strategy that involves recalling what was learned previously. It can take many forms, including flash cards, practice tests, and open-ended writing prompts, and helps learners recognize what they do and don’t know. The paper’s authors emphasize that people who check their responses for errors or get feedback right away learn even better.

“Forgetting is a very natural thing; you can’t stop forgetting even if you try, but you can slow down forgetting by using retrieval practice and spacing,” says Carpenter.

“Probably the number one misconception is that learning has to feel easy in order to be working, and that’s just not true at all. You’ll learn more durably and more effectively if you persist and get through those challenges than if it had felt easy the whole time,” says Carpenter.

Simply highlighting or rereading a textbook feels easier than writing responses to practice essay questions. But without the knowledge check that comes with trying to retrieve learned information, there’s a greater risk of being lulled into what the authors call an “illusion of learning.”