Using spaced repetition will help you remember things long-term
Spaced repetition, also called distributed practice, is one of the three primary teaching methods I train my tutors to incorporate into their sessions. It is one of the best ways to help you recall information and solidify it into your brain for the long-term – think final exam!
So what is spaced repetition? Well, the name kind of gives itself away – it’s the idea that in order to learn something you cover it once, then again, and again, and again until you get it. Sounds stupid and obvious, right? But here’s the key – you wait for longer and longer periods of time before trying to recall the information. This is called an expanding “spacing effect” in psychology and it has been shown to be much more effective in helping people learn new skills and recall information. Let me illustrate the method of spaced repetition with a simple example.
Let’s say you are studying for a biology quiz and need to recall parts of the cell and their functions – i.e. the nucleus contains DNA, ribosomes synthesize proteins, lysosomes breaks down cell waste, microfilaments help give the cell shape, etc. If you have 15 parts of the cell and their functions to memorize and you have them all on notecards (even though I have a better technique than notecards which I explain in my Active Recall article), here is what you would do: Look over notecard 1 and think to yourself “Okay, the nucleus contains DNA.” Then look look over 2 and say “Ribosomes synthesize proteins”, then try to recall 1 one again – “The nucleus contains DNA”. Then look over 3: “Lysosomes break down cell waste”, then try to recall the 2 and 1 one again. Look over 4, and then try to recall 3, 2, and 1 again. Then look over the 5 and try to recall the 4, 3, 2, and 1.
See what’s going on here? You are forced to recall the pieces of information over and over again, but with more time between each recall since you are adding another piece of information to the list each time. As soon as you think you have 1 down cold, then take it out of the running for awhile, set the notecard aside, and come back to it when you are on cell part 10, and then one more time when you are on 15. If you do this with all of your cell parts and keep going over them until you’ve got them, remove the ones you know from the running each time and come back to them towards the end, you will have them all memorized in no time. I know many of you have done something like this, perhaps with notecards, but most students miss some very key parts of this method, and doing it exactly right is important for maximizing efficiency and recall.
Here are what most students do: they make a stack of notecards and go through all of them before returning to the first card, usually 5-20 minutes later depending on how big the stack of notecards is. Some might stop after this and say “I’ll do it again later tonight or tomorrow”. A better student might go through them one or maybe two more times back-to-back, but then put them away and not come back to them until hours or even days later. This is spaced repetition in it’s most inferior form. Students know they need to go over things several times before the material sinks in but don’t have any idea how to go about it. The reason that doing it the standard way of plowing through a stack of notecards one-by-one and then putting them down and not coming back to them until later is because the brain’s physical processes of making new memories don’t work on this timeline. Using the latest scientific literature on spaced repetition and my own personal experience here are the 3 most important keys to this method.
Key 1: Spacing between recalls. It is important to keep the spacing between recalls shorter at first and then increase the spacing with each successive recall. Research has shown that if you need to remember something for several days to a month later, which is often the case for exams, your last recall should be at least a day after your second to last recall. If you want to remember something for an even longer period of time, maybe 2-3 months, you should space your last recall a few days or a week after the second to last recall.
Key 2: Adjust the method to fit your brain. Some students need to go over something 10 times before they get it and some students might only need to see it 3 or 4 times. Let’s say you need to remember some information for an exam in 2 weeks and you typically have to go over something 8 times before you remember it, then your spacing between recalls might go something like this: 15s, 1m, 5m, 15m, 1h, 3h, 1d, 3d. If your brain absorbs information quickly and you only need to see something 4 times before you’ve got it for good, you might use these spacings: 5m, 1h, 3h, 1d.
Key 3: Make sure you’re not just reading your notecards again each time. This is tremendously important! Just reading your notecards doesn’t help your brain build new circuits to store the information. You must use “Active Recall” if you want to actually remember the information. This means you must not be looking at the notecard or sheet of paper when you’re recalling what that the nucleus does – you have to force your brain to produce it from scratch. The notecards are a crutch, and your brain is a very lazy creature, as I’m sure you’ve noticed. It doesn’t want to form new memory pathways if it doesn’t have to and as long as it knows that it can use the notecard for cues it won’t do what it’s supposed to do, which is build a new brain circuit so you can recall the information without any help. You’re not going to have your notecards with you when you take the exam, so you cannot even be looking at them when trying to recall the information. It’s okay to take a glance at which part of the cell you’re on, but that’s it, look away before you recall what that cell part’s function is.
And that’s basically it. Spaced repetition is a very simple concept but you have to do it right to get the maximum benefit. One thing you might be thinking is “What am I supposed to when I’m waiting to go over the information again? Just sit there for the 5m, 30m, or 1 day?” Of course not! You can be a spaced repetition machine and be studying multiple things, or even multiple subjects, at once, just rotating them in when appropriate – like if you’re a blackjack dealer shuffling multiple decks of cards, you just shuffle and rotate them in until you’re finished.
For those of you really dedicated students, another great idea is to keep whatever set of notes or notecards you’ve just finished learning using spaced repetition and make a reminder to go over them again in a few days, and then a few weeks later. This will help you prepare for the final exam during the semester, and by the time that dreaded week rolls around, when your classmates are all curled up in the fetal position and crying for mommy to make it better, you’ll hardly have to exhaust a brain cell because you’ve been ready to take this test for weeks!
So what evidence do I have that this stuff works? Tons. This method was first introduced about 130 years ago by Hermann Ebbinghaus in his book Memory: A Contribution to Experimental Psychology. Since then there have been hundreds of studies confirming that this method works for just about every kind of recall and skill learning. Rather than referencing all of these articles, I have just referenced a great review article by Cepeda et. al.1 . It is a meta-analysis (fancy science talk for “We looked at everyone’s studies and lumped all the results together in one giant paper”), and in it they reviewed 830 assessments of spaced repetition from 317 experiments published in 184 different articles. These scientific studies included over 25,000 participants total and the data supporting spaced repetition as a more effective study method than conventional massed learning (all at once) is almost as hefty as the data supporting a round over a flat earth. Go ahead and check out the hundreds of articles they cite in their work if you’re not convinced. Their basic conclusion is the longer you need to remember something, the later your last recall should be. They indicated that one day minimum spacing is best for something that has be remembered for days or weeks, a typical exam studying timeline. People were able to remember as much as 30% more on tests they took 8-30 days later if their last repetition was 1 day after the previous one.
I understand that this news about spaced repetition being a superior studying technique might really suck for those of you who prefer to procrastinate and pull an all-night cram session before a big test, but if you want to benefit from this stuff, you really can’t resort to your cram sessions any more. Using spaced repetition might seem like it requires more time, but that’s not true – all the scientific studies made sure the total amount of time studying the material was the same, whether it was in one big chunk, or broken up into smaller, spaced out sessions. This method does, however, require a lot more discipline because you have to make sure you review the same material again, and that study session a day later is of critical importance. If you procrastinate and cram you actually end up putting in more time over the course of the semester since your brain can’t hold onto crammed information as well as material learned by spaced repetition, and you just have to do another exhausting cram for the final. If you plan to pursue a particular field of study you are always required to learn and remember certain fundamental concepts, so don’t cram for Pete’s sake! Take the time to do it right, and you won’t have to waste time relearning the material 5 times over. Not to mention you also put yourself under a lot more stress. What if you get sick during the day or two leading up to the exam? If you use spaced repetition this won’t provide a big obstacle for you, but if you’re counting on a highly-productive cram session to make the grade, well, good luck Sniffles.
So here’s the take-home message:
Spaced repetition is a far superior study method to cramming everything into one long study session. The literature is overwhelming to support a change in your study habits. The most important repetition is the one that’s at least 1 day later. Overall, this method will save you time and stress and you will remember information for much longer than your peers. Final exam, no sweat!
- Cepeda NJ. Pashler H. Vul E. Wixted JT. Rohrer D. Distributed practice in verbal recall tasks: a review and quantitative synthesis. Psychological Bulletin. 132. 3:354-380. 2006.