To improve your memory, try to get some space.
Imagine you have a big exam or work presentation at the end of the week. You’ll have to do it all from memory, so you have some studying to do. How should you decide how much to prepare? Do you practice everything once? Twice? More? It’s intuitive (and true) that more repetition results in stronger, more durable memories than less repetition. What’s less obvious is how much of a difference factors other than sheer quantity of practice can make.
In the late 1800’s, a pioneering German psychologist named Hermann Ebbinghaus discovered one such factor: certain schedules of repetitions are much more effective than others. He remembered information better when there was some time between his first and second exposure to it, compared to spending the same total amount of study time all at once. Although by today’s standards his methods were flimsy (he was his own — and his only — experimental subject), a huge amount of work by others has since supported and extended his findings.
This work has revealed a surprising but reliable pattern: if you have a limited amount of time to study or practice material you wish to learn, the best thing to do is not to spend that time all at once, but to spread it out into periods of study separated by breaks. For example, if you’re studying for a vocabulary quiz in four days, and you know you have two hours total in which to study, you’re better off studying for a half-hour on each of the next four days than you are studying for two hours all at once.
At this point you may be remembering your high school teachers insisting, “don’t cram!” In fact, cramming does seem to work for its intended purpose — passing an immediate test. If you need to learn information very rapidly, but do not need to know it for very long, cramming instead of spacing is probably fine. But don’t count on remembering what “crepuscular” means a month after you take that quiz! Instead, spacing is for the conscientious, the ambitious, for those who would like to learn and retain information for as long as possible.
And it’s not just for vocabulary. Spreading out your study or practice has been shown to help long-term memory for an impressive variety of subject matters. It helps for all sorts of verbal learning tasks[i], like recalling what you read in a book, or remembering how to say “eggplant” in Italian. (Melanzana.) Distributing practice can also improve your memory for matching names to faces[ii], or learning physics[iii], and for skills like spelling[iv], dance[v], learning a musical instrument[vi], and even performing surgery[vii]! What’s especially interesting is that although each of these areas have shown spacing effects — advantages in performance when practice or study is spaced, rather than crammed — not all of them rely on the same brain systems. Different neural mechanisms are responsible for how we learn material that we can easily talk about (like facts and words) and material we can’t so easily express (like how to stitch up a wounded patient or play “Chopsticks” on the piano). Why should types of learning that rely on different processes in the brain all be enhanced by a single, simple, manipulation?
Unfortunately, even though scientists have known about the spacing effect since the late 1800’s when Ebbinghaus first reported it, we still don’t know exactly how or why it works the way it does. Still, we have made some progress in developing a theory. Some scientists think that by adding space in between repetitions of the same information, we allow time for irrelevant details to fade away. Then, when that same information is presented again, we’ve forgotten the aspects that don’t matter, while the critical parts are repeated, and therefore reinforced. Others believe that the key is familiarity: when we cram, maybe we don’t fully process information the second or third time we see it, since our brain feels like it already learned it five minutes ago. So again, adding some time in between repetition allows us to forget, and forces our brain to put in its full effort. Still other scientists think that our mental representation (the way information is encoded in the brain) of the fact or skill we’re trying to learn is enriched by the surrounding environment. So if we study the same thing twice in the same environment, we only get that enrichment once. On the other hand, if we allow some time to pass before repeating it, it’s more likely that some aspect of our environment (even a small one like the ambient noise), has changed, potentially enhancing that mental representation. Ultimately, a fully satisfying explanation of the spacing effect remains elusive, but the pattern of results is clear: spacing helps you remember.
But how much does it help? And for how long? One impressive study[viii] taught college students a set of 50 Spanish words and their English equivalents on a schedule that repeated either all within one day (cramming), after a day had passed, or after a month had passed. They tested these students after eight years (!) and found that, although everyone had forgotten a majority of the words (eight years is a long time), those who repeated their study after a month, instead of within the same day, remembered two and a half times as many words! Just as fascinating, they remembered twice as many words as those who repeated their study after a day. So not only does spacing help memory, but more spacing is better than less spacing, at least as far as long-term recall is concerned. Some other research has compared spaced learning to crammed learning, but allowed the crammers to study for longer. This work[ix] found that even doubling the amount of study time when cramming is not enough to make up for the advantages that spacing provides; even with half the study time, it’s better to distribute your study than to cram.
With such impressive and wide-ranging results, educators, coaches, and instructors of all sorts must have been quick to adopt spaced practice, right? Unfortunately, they haven’t. “Neither American classrooms nor American textbooks appear to implement spaced reviews in any systematic way,” complains Frank Dempster, a researcher who studies spacing[x]. It is rare that an educational intervention has so much well-supported research behind it, so when the results are in, scientists want to see the findings applied to the real world, but so far they’ve been disappointed. Widespread adoption of spaced learning could improve fields as diverse as curriculum design, pedagogy, industrial training, music education, and athletics, but has not yet made the splash it deserves. This is not to say that you can’t help yourself using this technique. Next time you need to learn something, try spreading it out over time. It may feel more difficult in the moment, but you’ll hang on to the memory you build for much longer.
[i] Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin, 132(3), 354-380.
[ii] Xue, G., Mei, L., Chen, C., Lu, Z.-L., Poldrack, R., & Dong, Q. (2011). Spaced learning enhances subsequent recognition memory by reducing neural repetition suppression. Journal of Cognitive Neuroscience, 23(7), 1624-1633.
[iii] Grote, M. G. (1995). Distributed versus massed practice in high school physics. School Science and Mathematics, 95(2), 97-101.
[iv] Rea, C. P., & Modigliani, V. (1985). The effect of expanded versus massed practice on the retention of multiplication facts and spelling lists. Human Learning: Journal of Practical Research and Applications, 4(1), 11-18.
[v] Batson, G., & Schwartz, R., Eliot. (2007). Revisiting the value of somatic education in dance training through an inquiry into practice schedules. Journal of Dance Education, 7(2), 47-56.
[vi] Simmons, A., L. (2012). Distributed practice and procedural memory consolidation in musicians’ skill learning. Journal of Research in Music Education, 59(4), 357-368.
[vii] Mackay, S., Morgan, P., Datta, V., Chang, A., & Darzi, A. (2002). Practice distribution in procedural skills training: a randomized controlled trial. Surgical Endoscopy, 16(6), 957-961.
[viii] Bahrick, H. P., & Phelps, E. (1987). Retention of Spanish vocabulary over 8 years. Journal of Experimental Psychology, 13(2), 344-349.
[ix] Childers, J. B., & Tomasello, M. (2002). Two-year-olds learn novel nouns, verbs, and conventional actions from massed or distributed exposures. Developmental Psychology, 38(6), 967-978.
[x] Dempster, F. N. (1988). The spacing effect: A case study in the failure to apply the results of psychological research. American Psychologist, 43(8), 627-634.