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Four Things Scientists Get Wrong About Spacing Effects

You learn more by spacing learning across time, but here's when it doesn't work.

The spacing effect is unintuitive. The common misconception is that massed practice is better than spaced practice. In fact it’s the opposite: If you're going to study something twice (or more), you learn more by spacing the two study trials apart rather than massing them together. So don't study something 5 times on Friday, study it every day from Monday-Friday. You will learn more. The spacing effect is one of the strongest effects in the memory literature.

Once you learn about spacing, the pendulum often swings too far. More misconceptions immediately spring up that make spacing seem better than it is. I’m going to talk about four of them. These misconceptions aren’t just for novices: they seem to be common among researchers studying the spacing effect.

Misunderstanding 1: Spacing works at the level of topics

“When I study for my bio (etc.) exam, I tend to study (e.g.,) chapters 1-5 all in one night. Now I realize I should study one chapter per night instead.” In other words, spacing works for studying a topic.

The data do not support this idea. Nor do they refute it. It simply hasn’t been tested.

Spacing studies involve studying something repeatedly. It might be a definition, or fact, or text passage, or even variations on a single concept (e.g., gentoo penguin), but whatever it is, you study it twice or more. Studying chapters of a textbook is different because each chapter is different—it’s not a repetition.

There is strong evidence that if you’re going to study chapter 3 twice you should space it. But if you only study each chapter once, you are neither spacing nor massing because you are not repeating. (There will be some repetition because certain concepts—like DNA—will come up repeatedly, so hypothetically you should learn those concepts better if you space, but this idea hasn’t been tested.)

There are a few studies where the similarity between repetitions is very minimal. These studies show that when the participants don’t realize they’re seeing a repetition, spacing stops being beneficial. That’s exactly what you’d predict if repetition was a necessary ingredient in spacing effects.

Someone should do a study where non-repetitions are spaced or massed, for example asking participants to read 5 chapters of a book all on one day or across 5 days. Or how about this: does binge-watching an entire season of a TV show in 2 days lead to better or worse memory than watching one episode a week? But until these studies are done, it’s premature to recommend spacing of non-repetitions.

Misunderstanding 2: Spacing isn’t just about learning

“I’ve been massing when I do dishes, or laundry. Now I realize I should space.”

Not necessarily—spacing is just about learning. If you are trying to learn spacing is great, but learning isn’t always the goal. Spacing might mean you’ll be better tomorrow, but if you want to be good today, massing is fine (and sometimes good). So massing dishes is fine if you’re not trying to learn to do dishes.

Misunderstanding 3: Studying less is good because it means spacing more

“I was going to study for an hour each Monday, Tuesday, and Wednesday. Now I realize I can increase spacing, and learn more, by taking Tuesday night off.” In other words, spacing can mean that 2 hours of spaced studying are better than 3 hours of less-spaced studying.

Wouldn’t that be nice? Unfortunately there’s no empirical support for this one either. In spacing experiments total study time is held constant. Many studies have shown that studying more generally leads to more learning.

Misunderstanding 4: The value of studying lies in smart distribution, not studying more

Researchers often say this one: “We should recommend efficient study techniques, not more studying. The way many students do it, studying can lead nowhere.” Study smarter, not harder.

It’s true that studying with zero efficiency is a waste of time. But how common is that? I don’t think psychologists really research this question much; how many studies compare studying to not studying at all and find that they’re equally effective?

Furthermore, if I am going to recommend ways to study efficiently, like spacing, I think I can also recommend using them a lot. It’s like I’m giving someone a faster bike. Why not also tell them they’ll get farther by riding more. Like distance, learning = rate x time.


Spacing helps when you are studying something repeatedly, but there’s no evidence that it helps when each learning session involves different materials (e.g., different chapters). It won’t necessarily help if your goal isn’t learning. There’s no evidence that you should study less in order to increase spacing. Finally, there’s a simple equation: total learning = learning efficiency x time studying. Increasing efficiency is good, but if you do, studying more is good too.

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