A week of PSY 101.

Why cramming feels like it works

PSY 101 · Memory and how people learn · about 540 words

Most students have pulled an all-nighter before a test and done fine. So it is reasonable to ask why teachers keep warning against it. The answer is that cramming works for one thing, the test the next morning, and fails at the thing a course is actually for: remembering and using what you learned weeks later.

In the 1880s, the German psychologist Hermann Ebbinghaus memorized lists of nonsense syllables and tested himself at intervals afterward. He found that memory drops off quickly at first and then levels out, a pattern now called the forgetting curve. Much of what he learned was gone within a day or two unless he reviewed it. He also found that reviewing made the next drop-off slower. Each time he relearned a list, it took less effort, and it lasted longer.

This is the spacing effect: the same amount of study time produces longer-lasting memory when it is spread out over several sessions instead of packed into one. Two hours of review split across four days usually beats two hours the night before. The spacing seems to work because each return trip requires a little effort to bring the material back, and that effort is what strengthens the memory.

A second finding explains why rereading notes feels productive but often is not. In a widely cited 2006 study, psychologists Henry Roediger and Jeffrey Karpicke had students read a short passage. Some students reread it several times. Others read it once and then practiced writing down everything they could recall. Five minutes later, the rereaders did slightly better. A week later, the students who had practiced recalling remembered far more. This is called retrieval practice, or the testing effect: pulling information out of memory strengthens it more than putting it in again.

Rereading has a hidden trap. When you look at familiar notes, the material feels easy, and that feeling of fluency is easy to mistake for knowing it. Researchers call this an illusion of competence. A practice question removes the illusion quickly, because either you can produce the answer or you cannot.

Put together, these findings suggest a plain study routine that works in almost any course:

Start early and come back often. Short sessions spread across the week beat one long session at the end.

Test yourself before you review. Close the book, write what you remember, then check. The gaps tell you what to study.

Mix it up. Practicing different types of problems in one session, instead of twenty of the same kind in a row, feels harder but helps you choose the right method on a test. This is sometimes called interleaving.

Expect it to feel harder. Spaced, self-tested study often feels less smooth than rereading. Psychologists Robert and Elizabeth Bjork describe these as desirable difficulties: some struggle while learning is a sign the learning will last.

None of this means a student who crams is lazy or that the night-before session is useless. It means the timing matters. In an online college course with a weekly schedule, nobody reminds you to start on Monday. The students who do well usually are not the ones who study the most hours. They are the ones who spread the hours out and check themselves along the way.

Sources: H. Ebbinghaus, Memory (1885); H. L. Roediger and J. D. Karpicke, "Test-Enhanced Learning," Psychological Science (2006); E. L. Bjork and R. A. Bjork, "Making Things Hard on Yourself, But in a Good Way" (2011).