The Spacing Effect: Why Cramming Fails (and What to Do Instead)

The night before an exam, cramming feels like the responsible thing to do. And it partly works: you can hold a lot in your head until tomorrow morning. The problem is what happens after tomorrow morning.

The forgetting curve

In the 1880s, the German psychologist Hermann Ebbinghaus spent years memorising lists of nonsense syllables and testing himself on how much he remembered over time. He found that forgetting follows a steep curve: most of what you learn in one sitting fades within days, and then the loss slows down.

He also found something more useful. When he relearned a list, it took less effort than the first time, and the relearned list faded more slowly. Each return to the material flattened the curve.

The spacing effect

Put those together and you get one of the most reliable findings in all of psychology: the spacing effect. The same amount of study, spread out over time, leads to much better long-term memory than the same amount crammed into one session.

It has been shown with words, facts, maths, skills and motor tasks, in children and adults, in labs and classrooms, over more than a century.

Why spacing works

The leading explanation is that a little forgetting is good for you.

When you study something you’ve just seen, it’s still fresh, so bringing it to mind takes almost no effort, and the memory barely gets stronger. When you come back after a gap, you’ve partly forgotten it. Working to recall it strengthens the memory far more.

That’s also why spacing feels worse while you’re doing it. Cramming feels fluent: everything is familiar. Spaced study feels effortful: you keep half-forgetting things. The effort is the point.

Why cramming feels like it works

• You’re tested soon after. If the exam is tomorrow, cramming can get you through it. The cost shows up next week, next term and in any later course that builds on it.
• Familiarity feels like knowledge. After hours on the same material, it all looks familiar, and that’s easy to mistake for knowing it.
• It feels productive. A long session feels like hard work, whether or not it lasts.

How to space your study

You don’t need a perfect schedule. Any spacing beats none.

1. Start earlier, study shorter. Four one-hour sessions across two weeks beat one four-hour session the night before.
2. Come back after a gap. A good rule of thumb: review a topic a day after you first learn it, then a few days later, then a week or two later.
3. Stretch the gaps as it sticks. Each time you get it right, wait longer before the next review. Each time you struggle, come back sooner.
4. Test yourself when you come back. Spacing works best combined with retrieval: try to recall it before you look at your notes. More in the study technique that beats rereading.
5. Sleep in between. Sleep helps consolidate what you learned that day. An all-nighter trades that away.

How much gap?

It depends on how long you need to remember something. Research suggests the best gap between study sessions is roughly 10 to 20% of the time you want to remember it for. For an exam in a month, gaps of a few days work well. For something you want to know for years, the gaps can grow to weeks and months.

Where this shows up in Cognosc

Cognosc is built on the spacing effect. After you learn an idea, it checks back with one quick question, just before you’d be likely to forget it. Each time you get it right, the next check comes further away.

Check your study habits

The free how learning works test asks about cramming, rereading and eight other study habits, and shows what the research says about each.