Research School Network: Interleaving: More Than Just Mixing Things Up There are benefits to interleaving, but before you do more mixing than Fatboy Slim on Bake-Off, consider your approach.

Knowledge about cognitive science has grown over the last few years. As terms like ​‘retrieval practice’, ​‘dual coding’ and ​‘interleaving’ become more widely used, there are also instances where some opportunities are missed by a limited understanding. This is the second in our series of posts. Last time, we looked at retrieval practice, and today we look at interleaving.

“Interleaving occurs when different ideas or problem types are tackled in a sequence, as opposed to the more common method of attempting multiple versions of the same problem in a given study session (known as blocking).” (Weinstein Y, Madan CR, Sumeracki MA, 2018)

Often, the way that interleaving is conceptualised is ​‘mixing things up’, but there is more nuance to it than that, and there are instances where interleaving is optimal and some where it wouldn’t be welcome at all!

Discriminating Contrast

In one experiment on the effects of interleaving, Kornell and Bjork (2008) asked participants to study paintings, 6 each by 12 artists. Some were asked to block their study i.e. look at each artist’s paintings consecutively and others had them interleaved. Despite participants’ own belief that the first strategy would be the most successful, it was not. The second group could identify more and also knew more about the artists’ styles. Other studies have looked at distinguishing between birds, psychological disorders and many more.

So the research shows that interleaving works well when distinguishing between similar content, what we call discriminating contrast. As David Didau writes, in his excellent What if Everything you Knew About Education Was Wrong?, ​“When you only practise one skill over and over, the brain knows what is coming next and doesn’t have to work as hard. With interleaving, the brain is forced to figure out what each skill each practice problem calls for.”

A subject that can benefit from this is Mathematics. Imagine a class has been studying area and have just looked at the areas of triangles. Often, they will practice several examples to calculate area, generally with an iterative approach leading to increasing difficulty. This can lead to fluency but one crucial part is neglected with this process – the need to discriminate between problem solving strategies. ​‘What type of question is this?’ is already answered. It might be more effective to interleave the area problems with other superficially similar ones using triangles e.g. perimeter, angles, trigonometry.

Craig Barton’s ssddproblems.com is a website with many examples of questions like these which ask pupils to choose between strategies. ​“By exposing students to problems like that, I would ensure that they learned to recognise not just the similarity between problems, but also the differences between them.”

This might also have applications for any subject where choices have to be made about strategy, but where massing all the practice creates an illusion of mastery.

Be careful when you interleave

Mixing things up can have disastrous consequences in certain circumstances. For example, there is no point in introducing the SSDD problems before any of the strategies and methods have been introduced. Similarly, English Literature students beginning their initial study of Macbeth on Monday, Animal Farm on Tuesday and A Christmas Carol on Wednesday may well find that they struggle. It is likely that with nothing stored in long-term memory, they are overwhelmed. However, once the material is taught, it would make sense to interleave the study of that material.

We also have to be careful with managing pupils’ motivation. While a certain amount of difficulty is optimal in producing effective learning, too much and we introduce failure and the belief that something is too difficult. Pupils self-efficacy, the belief that they will be successful at a given task in the future, is correlated with a number of factors including academic performance. Interleaving at an early stage may not only be unsuccessful, but bring the idea of failure to that area.

Didau, D (2015) What if Everything you Knew About Education Was Wrong? Crown House Publishing
EEF (2013) The impact of non-cognitive skills on outcomes for young people literature review.
Kornell N, Bjork RA (2008) Is Spacing the ‘‘Enemy of Induction’’? Psychological Science 19:6
Rohrer D. (2012) Interleaving helps students distinguish among similar concepts. Educational Psychology Review 24: 355 – 367.
Weinstein Y, Madan CR, Sumeracki MA (2018) Teaching the science of learning. Cognitive Research: Principles and Implications 3:2