Spread it out: why study sticks better over several days

Spread it out

It’s the night before. You sit with your notes for 3 hours, and by the end it feels like it’s in. A week later, a lot of it is hard to find.

Spaced practice uses the same time differently. You study a topic, leave it, then come back to it on another day. Then once more, a few days after that. Each visit can be short.

What the research found

Study spread over time tends to be remembered better than the same study in one block. In 2006, Cepeda and colleagues pooled 839 results from 317 experiments on remembering words and facts. They looked closely at timing: the further away the test, the longer the best gap between study sessions.

A 2008 study by the same team tested more than 1,350 people. They learned a set of facts, reviewed them after a gap of up to 3.5 months, then took a final test up to a year later. As the gap grew, results rose, then fell only slowly. For a test a week away, the best gap was about 20 to 40% of that time. For a test a year away, it was about 5 to 10%. Our rough sum: for an exam a month away, review about a week after you first study.

Kapler and colleagues tried it closer to real study in 2015. They gave 169 university students a mock lecture on a science topic. The students reviewed it online either 1 day or 8 days later. Tested 5 weeks after their review, the 8-day group did better on both fact questions and questions that asked them to use what they’d learned.

The 2013 review by Dunlosky and colleagues rated 10 common study techniques. Spacing was one of only two rated highly useful, beside testing yourself, partly because it has helped learners of different ages and abilities.

You don’t need perfect gaps. A 2021 meta-analysis of 29 studies by Latimier and colleagues found that spaced practice tests clearly beat back-to-back ones. Gaps that grew longer each time were not clearly better than even gaps.

Does it work with ADHD?

We couldn’t find a study that tested spacing with people who have ADHD. This rests on research with people in general, mostly on facts and words, so treat it as a good bet rather than a proven fix.

There are practical reasons it may suit ADHD. A 3-hour sitting asks for a long stretch of attention. Three 15-minute reviews ask for 15 minutes at a time, each with a clear start and finish. The hard part is remembering to come back. That’s the part to hand to a list.

How to do it

• Pick one topic you’ll need in a few weeks.
• Study it once. Then put two short reviews on two later days, a few days apart.
• At each review, close the book and write what you remember, then check.
• If a review slips, do it the next day you can.

Try this week

Choose one topic from this week’s classes. Review it today, again in 2 or 3 days and once more next week. Put the three days in your to-do list or calendar while you’re thinking of it. Each time, recall first, then check your notes. If a review gets missed, that’s fine. Do it when you next can: the gap doesn’t need to be exact.

Three reviews, three days

The to-do list shows in the full layout, with or without an account.

1. Open Planned in the to-do list. Type a review and end it with a day, such as ‘Review cell biology Thursday’. The date shows under the box. Press Enter. For any other day, press Date, then Pick a date. Give each review its own day.
2. On the day, open My Day. The review is waiting under Due today. Press Add to My Day.
3. Signed in, pick the subject under Subject (+ new adds one). Choose 15m (or Custom for a shorter run), then press Start on the review’s row.
4. At zero a short chime plays, and the run’s time adds up on the task. When the review is finished, press Mark done beside Last run, above Start focus.

Planned shows what’s coming under Today, Tomorrow, This week and Later. A review you didn’t get to moves to From before. Nothing turns red and nothing is counted. For a subject that lasts all term, tap a review’s name and set Repeat to Every week: ticking it done makes the next one, a week on. Signed in, Topics later shows the time and average run for each subject.

Cramming feels like it works

In 2009, Kornell had people learn vocabulary word pairs with flashcards on a computer. Across his experiments, spreading out each card’s repeats beat bunching them close together for 90% of people. Yet after the first session, 72% believed bunching had worked better. Bunched study may feel smooth because the answers are fresh. Coming back after a gap feels harder, because some of it has slipped. That feeling isn’t a sign it’s failing. It’s one paper, about word pairs rather than a whole course. It wasn’t about ADHD.