Active recall: test, do not re-read
Active recall means trying to retrieve an idea from memory instead of looking at it again. Close the book and ask yourself the question. The act of struggling to remember, even when you half-fail, is what strengthens the memory. Re-reading skips that struggle, which is exactly why it feels easier and works worse.
In practice, active recall looks like:
- Turning your notes into questions and answering them from memory.
- Explaining a topic out loud, as if teaching it, before checking what you missed.
- Redoing a problem from a blank page rather than following a worked example.
Spaced repetition: revisit before you forget
You forget on a curve: fast at first, then slower. Spaced repetition means reviewing a topic just as it is about to fade, then leaving a longer gap before the next review. Each successful recall resets the clock and makes the memory last longer, so the reviews get further and further apart until the idea is effectively permanent.
A simple schedule for a new topic: review it the next day, then after three days, then a week, then two weeks. If you get one wrong, shorten the gap and build back up.
Why it feels harder (and why that is good)
Both methods feel worse than highlighting because they involve effort and the occasional blank. Researchers call this "desirable difficulty": the effort is not a bug, it is the mechanism. If a study method feels effortless, it is probably building recognition, not recall, and recognition is not what the exam tests.
So trust the discomfort. A study session where you struggled to remember and then checked your answer will beat an hour of smooth, pleasant re-reading almost every time.