The Key to Interleaving: Jumble It Up!

The Key to Interleaving: Jumble It Up!

By: Megan Smith, Yana Weinstein, & Fergus Dark

Interleaving can be a tricky concept and is often confused with spaced practice. In laboratory studies, we can disentangle the effects of interleaving and spacing to show that they are both helpful on their own to produce learning (1), (2). However, in classroom practice, it can be difficult to implement interleaving on its own, without spacing. Interleaving often creates spacing, and spacing can at times create interleaving. This, of course, isn’t a bad thing. Both tend to improve learning, and research shows that combining many of the 6 key strategies from cognitive psychology can be the most powerful ways to promote learning. All of this said, we argue that it is still important to understand and utilize interleaving, especially when teaching subjects that involve problem solving (e.g., math, physics).

So, what exactly is interleaving?

An anecdote may shed some light. We recently (June-July 2017) visited a number of schools and school alliances in England to run workshops on the science of learning. One of the places we visited was Samuel Ward Academy Trust, and while there we spent an hour with around 20 students ranging from 9 to 18 years old. We asked the students to tell us what they do to help themselves learn. We did this before even mentioning names or explanations of the strategies so that we could later link the strategies to concrete examples of things the students were already doing.

One student, Fergus Dark, brilliantly explained how he “jumbles it up” during learning. What he was describing was a lot like interleaving, though he was calling it something else. (We actually think the term he used is more easily understood than "interleaving"!) We love the phrase “jumble it up”, and asked him to write out his explanation. Here is his description in his own words:

“Jumbling is a memory technique for recalling information. Often when revising, you learn key points, terms or information in a certain order. So when it comes to the exam you will remember it in that order. The paper may ask you to write it out in a different order or perhaps only ask for one key point. This is when jumbling comes in handy. Instead of spending time and effort trying to rearrange the info and possibly losing marks, when revising practice recalling the information in separate chunks and do not get to know it in the order laid out in front of you. Once you have nicely jumbled it all up in your head and can remember each section separately and quickly, then you`re good to go!” – Fergus Dark, Year 8 (7th grade equivalent) student from Thomas Gainsborough School in Great Cornard, England.

(Note: this blog may help Americans translate some of the technical terms from the UK Education system to the American Education system.)

Fergus used the example of learning how to give directions in German to explain his jumbling technique to us. At first, you learn how to give the directions in a certain order. For example, you might learn how to say turn right, then learn how to say turn left, and then learn how to say go straight. However, when you’re actually using these phrases, you want to be able to recall them in different orders. So during practice, you should jumble up the order of the German directions. This will make it easier to use them later on.


Most of the research on interleaving has focused on three different activities: jumbling up math problems (3), (4), (5); learning how to categories things (6), (7); and performing motor skills (8), which is less relevant to this post. In the math domain, the idea is that jumbling up the problems helps students learn how to solve the different problems and also when to apply various problem solving techniques (1). It helps students more flexibly use the information they've learned. In the categorization domain, the idea is to compare things from different categories; for example, paintings by Dalí, Monet, and Picasso all mixed up together rather than first looking at paintings by one painter, then the other. In this situation, jumbling it up helps students to be able to later match new paintings they've never seen to the correct artist (6).

Fergus, without realizing it, is applying this jumbling technique to foreign language learning. The field doesn't yet have much research on whether jumbling works in domains other than problem solving or categorization, and how similar or different the ideas should be for jumbling them up to work; though, one paper does suggest that jumbling up completely different things (in this case, anatomy terms and Indonesian vocabulary!) does not help learning (9). More research is needed to figure out what can be interleaved, and when interleaving might not help - and we're working on it!

What's so great about this anecdote is that it shows how helping students learn effectively is compatible with letting students take control of their own learning! Students do need direct instruction, especially when they’re novices (see this blog and this digest). But in this case, Fergus was already doing something that has evidence supporting its effectiveness - he was just unaware that what he was doing had an official name, "interleaving", and was being scientifically studied. In fact, many of the students mentioned things that were similar to the strategies, and we were able to link what they were doing to the evidence and provide suggestions for how to make their learning sessions even more effective (of course, they also mentioned doing things that were less effective, and we gently guided them towards alternatives and talked with them about some of the problems with intuition). This also highlights the need for future research on how to apply some of the strategies in different contexts, and it helps us identify areas where we need more evidence to support students' learning.

After their session with us, the students met with a few of their teachers for a debrief. The teachers asked them to write down their impressions of the session, and these were then later shared with a larger group of teachers from the same schools, just before they had their session with us. In their feedback, the students begged their teachers to implement the strategies into their teaching, and scaffold the students to use them! Overall, the students seemed really excited about the strategies, and the idea of studying more effectively - and their enthusiasm also motivated their teachers to commit to helping them study effectively. Win-win!


(1) Rohrer, D. (2012). Interleaving helps students distinguish among similar concepts. Educational Psychology Review, 24, 355-367.

(2) Carvalho, P. F., & Goldstone, R. L. (2014). Effects of interleaved and blocked study on delayed test of category learning generalization. Frontiers in Psychology, 5.

(3) Taylor, K., & Rohrer, D. (2010). The effects of interleaved practice. Applied Cognitive Psychology, 24, 837-848.

(4) Rohrer, D., Dedrick, R. F., & Burgess, K. (2014). The benefit of interleaved mathematics practice is not limited to superficially similar kinds of problems. Psychonomic Bulletin & Review, 21, 1323-1330.

(5) Rohrer, D., Dedrick, R. F., & Stershic, S. (2015). Interleaved practice improves mathematics learning. Journal of Educational Psychology, 107, 900-908.

(6) Kornell, N., & Bjork, R. A. (2008). Learning concepts and categories: Is spacing the “enemy of induction”? Psychological Science, 19, 585-592.

(7) Birnbaum, M. S., Kornell, N., Bjork, E. L., & Bjork, R. A. (2013). Why interleaving enhances inductive learning: The roles of discrimination and retrieval. Memory & Cognition, 41, 392-402.

(8) Lin, C. H. J., Chiang, M. C., Knowlton, B. J., Iacoboni, M., Udompholkul, P., & Wu, A. D. (2013). Interleaved practice enhances skill learning and the functional connectivity of fronto‐parietal networks. Human brain mapping, 34, 1542-1558.

(9) Hausman, H., & Kornell, N. (2014). Mixing topics while studying does not enhance learning. Journal of Applied Research in memory and Cognition, 3, 153-160.