If I gave you these numbers, how many times do you think you would need to recite them before you’re able to retain them for the next few months? Maybe a few times today, then again tomorrow and at the end of the week—and then a couple of weeks from now, then a month, and hopefully you’ll be able to remember them by then.
But what if you had 40 of those numbers, or 100 of them?
How long would it take for you to repeat them until you can remember all of them a few months from now? Probably quite a lot of times!
We’re talking about spaced repetition, which means revising pieces of information over time (for example, at the end of every week). There is a lot of research to show that spaced repetition is effective—but how effective? And can we make it even more effective?
Expanding gap spaced repetition and the Leitner System
One variation of spaced repetition is expanding-gap repetition, which means that the gap between each repetition gets longer and longer each time. It’s better than fixed spaced repetition because it increases your chances of forgetting, which means that it’s more likely to stick when you revise the information again.
Serious Limitations of Spaced Repetition
However, spaced repetition, in general, has some serious limitations that basically every high-level student knows of, yet no one really seems to be talking about.
First, the technique that you use to revise at each time point makes a really big difference.
For example, simply re-reading or re-writing the content produces shallow levels of learning because this is a form of PASSIVE learning (i.e. there’s not a lot going on in your brain).
There are a lot of other principles that you can incorporate, such as active recall.
‘Active’ means that you’re engaging your brain, and ‘recall’ means that you’re bringing the information out from your memory rather than relying on rereading it. This is more effective than passive learning—and if you’re using active recall on top of spaced repetition, that’s even more effective.
Of course, this is the same thing that everyone else talks about.
We already know this from the hundreds of YouTube videos out there from every ‘study guru’ who talks about it. But this is really only the beginning—because several other techniques are even more effective than active recall!
For example, there are constructivist methods of learning and revising, which involve active recall and active reconstruction (tests you not only on one specific piece of information but also on that piece of information in relation to other pieces of information). This means that you’re able to revise batches of information all at once, and your retention of each batch becomes greater because they’re all related to each other.
The Importance of Relational-Priority Learning
We talk about this idea of information-priority versus relational-priority learning very often. There are many techniques you can use for this.
Teaching, for example, is a highly effective revision technique—but even within teaching, there are certain methods of teaching that use more of this constructivist tendency by rearranging the information in a particular way.
In our program, we teach a student variation of the ‘whole part whole’ framework. Using this framework allows your revision to be a lot more effective.
The way you revise should also be different each time. It should use many different types of learning, something called multi-modal learning, and challenge retrieval and encoding from multiple different ‘angles’, a process called interleaving.
This means that you’re not just studying the same thing over and over again, but you’re studying multiple variations of it from multiple different angles. Not having interleaving is one reason why a lot of students get stumped by curveball questions—because that curveball is a variation of the concept they studied, and they didn’t practice those variations. A good revision strategy should be varied, it should have interleaving, and it should be constructivist.
However, there are some even more important limitations to consider for spaced repetition: the amount of revising you need to do becomes unsustainable if you constantly forget things.
To explain this, let me talk to you a little bit about the basis of spaced repetition, which is something called the Ebbinghaus forgetting curve.
The Forgetting Curve
The Ebbinghaus forgetting curve says that you will initially forget it very quickly when you learn new information. Still, the rate of forgetting (knowledge decay) gets slower each time you revise it. However, Ebbinghaus forgetting curves are for information that is purely memorised—it doesn’t consider information learnt with a relationship priority.
For example, the numbers that I gave you at the beginning of this post exist in isolation, so they follow the Ebbinghaus forgetting curves: you will forget them very quickly initially, and then a little bit slower, and then slower. Without looking back, do you still remember the numbers?
That’s why spaced repetition works.
But what’s even more effective is bypassing the need for frequent spaced repetition in the first place by adjusting the slope of this forgetting curve. We can do things so that the very first time you learn something, your forgetting happens at a much lower rate. This means that your retention is still very high even one month later—maybe at 90%, as opposed to 50% or less.
The most powerful thing you can do is not even need to revise because you didn’t forget it to begin with—which seems like it’s only possible if you’re a genius. In reality, it’s actually very consistently doable for most students, as long as you have at least a moderate level of intelligence. The best part is that we’ve seen these techniques also work for people with learning disabilities such as dyslexia and ADHD. It’s just the way that our brains are programmed!
So how do we modify the curve to forget things a lot slower and retain them a lot longer? We do this through relationship-priority learning. When you view information in isolation, you end up having bits of information that you’re trying to rote learn through repetition, which naturally takes a lot of time. The better method is to view information through relationships, which is what we teach in the program; that way, you don’t need to revise as much or as often. You can get away with revising once at the end of the month, and that tops up your retention and keeps it going until exams.
You’ll only find spaced repetition effective if you’re not using it at all.
If you are using it, you’re probably already experiencing some of its limitations. Its biggest limitation is that it’s not sustainable in the long term: having high levels of spaced repetition relies on always memorising and repeating information, which isn’t mathematically scalable because it increases your workload every day.
The much more effective solution is modifying the Ebbinghaus forgetting curves—and then you can add expanding-gap spaced repetition on top of that. The difference is that now it’s much more manageable because the amount you need to revise is much less.
You’ll be surprised at how much time you can actually save once you stop relying on spaced repetition.
The thing is, there are actually many study techniques, strategies and approaches out there that are more effective than just active recall & spaced repetition. It’s an entire field of research that we’ve been neck-deep in for years. If you’re new to this, I highly recommend reading our article on utilising Bloom’s Taxonomy to upgrade your learning.