Does spaced repetition help learn vocabulary?

Anyone who has crammed for a vocabulary test knows the feeling: you can recite twenty words on Thursday and remember five by the following Wednesday. Spaced repetition is the idea of fixing this by bringing words back after gaps. This article looks at what the research says, where it is mixed, and what a family can do with paper cards.

What is spaced repetition?

Spaced repetition means reviewing something several times, with gaps in between, instead of all in one sitting. Researchers usually call the opposite "massed" practice. Apps often schedule reviews automatically, bringing a word back shortly before you would be likely to forget it. You can do the same thing with a shoebox of cards.

What does the broad research say?

The most-cited review of the topic is a 2006 meta-analysis of distributed practice in verbal recall tasks. It pulled together 839 assessments from 317 experiments in 184 articles. Its key finding was that the gap between study sessions and the length of time before the test interact: the study gap that produces the best long-term recall gets larger as the time you need to remember gets longer (Cepeda and colleagues). Put simply, if you want a word to last a week, a shorter gap suits; if you want it to last months, a longer gap tends to suit.

That review covered recall tasks broadly, not only foreign words, and it is a general guide.

What about second-language vocabulary specifically?

Second-language studies mostly point the same way, but the details differ.

• Attention. In a 2019 eye-tracking study, adult English speakers read Finnish words inside English sentences. Repeated exposures that were spaced were remembered better than massed ones, and the spaced words received more attention while reading, which partly explained the advantage (Koval, 2019).
• An online replication. A 2025 study tried to repeat an earlier lab experiment on Swahili-English words with gaps of one to 14 days. Spaced groups did better than the massed group, as in the original. But the authors report that which gap was best depended on how the data were analysed, that about 61 per cent of recruits dropped out, and that the prior literature disagrees about gap length (Rogers, Nakata and Chiu, 2025).
• In a classroom. Ninety first-year high school students in Japan learned English verb-noun combinations on three schedules. The group that studied a set every day and repeated it every week made the biggest gains on both studied and unstudied combinations. But that group scored lower than the others during the learning phase, and the groups were not matched on proficiency (Yamagata, Nakata and Rogers).

So: spacing usually helps, there is no single best interval, and doing it can feel harder, which is part of why people avoid it.

Why does cramming feel like it works?

In the classroom study above, the group that practised on a spread-out schedule actually scored lower than the other groups while they were still learning, and made more over-extension errors, even though they came out ahead later. The authors flag this in their limitations. It fits a wider idea in the field that practice that feels smooth is not always practice that lasts, though we only read one study on it here. For a parent this is useful. If your child struggles a little when a word comes back after a few days, that is not a sign the method has failed. It may be part of how it works, though one study cannot prove that for every child.

What are the limits?

• The studies we read involved adults and school students. We did not find a readable source testing a particular schedule with young children, so we do not claim one.
• Lab words are not the same as the words a child meets in a story, a conversation or a song.
• Spaced practice helps remembering. It does not replace using words in sentences or speaking with people.
• A schedule that is too clever to follow does not help anyone.

How can a family use it without an app?

A simple version with paper cards:

1. Write the new word on one side of a card and its meaning on the other.
2. Keep three piles or boxes: new, learning, known.
3. Test the new pile first. Right answer: move to learning. Wrong: stay.
4. Test the learning pile a few days later. Right: move to known. Wrong: back to new.
5. Test the known pile about once a week or less, and move any wrong ones back.

The numbers of days are your choice. The research says gaps tend to help and that longer gaps suit longer-term memory, but it does not hand you an exact timetable. Choose days that fit your week, and keep sessions short.

The same method can be tried for Japanese and Mandarin characters; see our piece on writing systems. Families keeping a home language going may also like our piece on heritage languages. And since a larger vocabulary supports understanding, our article on how many words you need explains why the numbers matter.

How does this fit with XLingo?

In XLingo, words a learner has met join a review deck and come back on a spaced schedule, next to word cards, short grammar tips, practice and stories. It makes no promise of results. See the price and free trial.