Massed practice is how I learned math growing up; that is, focusing on specific problems. On Monday, my teacher gave me 20 addition problems. The next night she gave me 20 subtraction problems. Wednesday night was multiplication, and Thursday was division. Quiz Friday on everything I learned in the week.
The problem is that this method of teaching doesn’t optimize the durability of learning. Interleaving is the art of “mixing things up”. Maybe my teacher could have put in some addition problems mixed in with the subtraction problems. Toss in both addition and subtraction in the multiplication problem set. The night before the quiz, I should have been practicing all four skills I had learned, not just zeroing in on one.
Years of cognitive science research have established that interleaving – simply re-arranging the order of retrieval opportunities during spacing without changing the content to be learned – can increase (and even double) student learning.
Agarwal, Location No. 2,333
At the heart of interleaving is a subtle culprit that isn’t always given due credit – deciphering. If the learner needs to identify which tool set the problem demands before leveraging the tools, learning is strengthened. This may sound uncomfortable for the learner – and it is! – but that’s the point. Marathon runners don’t get faster by jogging at a comfortable pace.
When you let the memory recede a little, for example by spacing or interleaving the practice, retrieval is harder, your performance is less accomplished, and you feel let down, but your learning is deeper and you will retrieve it more easily in the future.
Brown, p. 75
After all, what good is it knowing something when you don’t know when to use it?
As a student, I could have (and should have!) used flashcards to practice interleaving. I could have created twenty addition flashcards the first night, shuffled in twenty subtraction cards the next night, and so on for the next two nights. As a student, I could have leveraged interleaving in my learning. But, me being me, I would have made the classic mistake of jettisoning cards too early.
Students should keep cards in their deck until they’ve retrieved it correctly three times. Just because a student has retrieved an item once doesn’t mean they “get it.” We know from research that students have a tendency to remove their cards too early, so by ensuring that students keep a card in their deck three times, students are accountable for making sure they really know it, rather than simply thinking they do. This also helps add space between cards in the deck (what scientists call lag), further increasing learning.
Agarwal, Location No. 4,839
While flashcards aren’t the only way to practice interleaving, it is a cheap and quick way to do it. I mean, who doesn’t like the idea of a fresh pack of stiff index cards and a Sharpie? There are tools that teachers and students can use, too. I like Quizlet because I can create cards, my students can create cards, we can share them with each other, and the content can be consumed in a variety of ways (traditional flashcards, matching games, “Learn” mode, and “Test” mode).
Remember to warn your students that interleaving might not feel good.
We harbor deep convictions that we learn better through single-minded focus and dogged repetition, and these beliefs are validated time and again by the visible improvement that comes during “practice-practice-practice.” But scientists call this heightened performance during the acquisition phase of a skill “momentary strength” and distinguish it from “underlying habit strength.” The very techniques that build habit strength, like spacing, interleaving, and variation, slow visible acquisition and fail to deliver the improvement during practice that helps to motivate and reinforce our efforts.
Brown, p. 63
As I look to do better with interleaving, I fear that the overhead I’ll incur in restructuring assignments, reframing my conversations, and creating Quizlets will be enormous. But I try to remember that teaching is a process; it’s never finished. Perfection isn’t an end product – it’s a mentality that encourages constant improvement. So I’ll make incremental improvements; I’m okay with spacing things out.
- Agarwal, P. K., & Bain, P. M. (2019). Powerful teaching: Unleash the science of learning. John Wiley & Sons.
- Brown, P. C., Roediger III, H. L., & McDaniel, M. A. (2014). Make it stick. Harvard University Press.
- Cover image by AnnasPhotography via Pixabay
