Interleaving Demystified
Jonathan Firth's Memory & Metacognition Updates #96
Hello! I’ve mentioned interleaving a few times lately, and I thought I was well overdue a deeper discussion of this. After all, it was my PhD topic! It is also:
Considered a desirable difficulty (see update #10);
One of the Learning Scientists’ six strategies for effective learning;
Endorsed (largely) by Dunlosky et al. (2015; see update #16);
An area that many teachers find confusing, according to InnerDrive’s blog.
All in all, interleaving is a key strategy for applying cognitive science to teaching and learning, but one that appears to need some demystifying!
What is interleaving?
Interleaving occurs when we directly contrast items from different categories, such as:
examples of different processes,
pictures from different categories,
different math skills,
etc.
The default approach in education is to have multiple similar items together, such as a set of problems/questions all focusing on the same concept or skill. Interleaving upturns this, saying that instead of like with like, we should put like with unlike.
For example, if you were teaching students about coral, the obvious thing to include in a lesson would be lots of examples of coral. To apply interleaving would mean contrasting images of coral with things that students might mix up with coral, for example plants with branchlike features, or rocks. This would help them recognise an image of coral when they see one in future.
As another example, if studying when to use prepositions (over, on, above, etc), interleaving would involve directly contrasting their use.
In sum, interleaving involves alternating or shuffling short items, like quiz questions or brief verbal examples.
What isn’t interleaving?
It’s also important to understand what interleaving is not. It does not mean mixing up entire topics in the same lesson or study sessions (for example, 30 minutes on rainforests followed by 30 minutes on human organs in the same Biology lesson).
Unfortunately, much advice on interleaving misleadingly suggests that this is a good idea!
Interleaving also does not mean mixing up topics or subjects in the same independent study session. The research on interleaving does not support a student studying Geography, Biology and Psychology all in the same evening, for example. None of the key research studies on the technique tried this.
(And hey… you might have noticed that I just contrasted some examples and non-examples of interleaving. To really interleave them, I’d have alternated the two, rather than having them in two sections. But this is a newsletter, not a lesson!).
The reason interleaving helps
Interleaving is helpful because it draws learners’ attention to the meaningful contrasts between different concepts or processes. When we see like with unlike, it becomes easier to see how two things differ.
To put this another way, learners get a better idea of the boundaries of a schema, helping them to correctly categorise new examples in future (i.e., to transfer their learning).
As touched on already, interleaving is considered an evidence-based strategy, with a pretty large effect size (Brunmair & Richter, 2019; Firth et al., 2021).
However, this depends on using it correctly, which includes choosing the right things to contrast. The issues are well explained in the accessible research paper below:
Carvalho, P. F., & Goldstone, R. L. (2015). What you learn is more than what you see: What can sequencing effects tell us about inductive category learning? Frontiers in Psychology, 6, Article 505.
I’ve also discussed interleaving with Bradley Bush of InnerDrive and Sarah Cottinghatt of IRIS Connect. You can watch our conversation on YouTube here:
Enjoy!
Overall
Interleaving can help because it establishes conceptual understanding, boosting transfer to new situations. Next time I will provide a simple step-by-step guide to make it easier for you to put this into practice in your teaching.
And all the best for the coming week,
Jonathan
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