The Emotional Learner

We know timing is important for learning. But time isn’t just about the duration of short-term and working memory; it’s also the spacing out of learning so that we can exploit the way we retain learned information. We call this the spacing effect.

A related phenomenon concerns the order in which we present information. For example, if I were to teach a topic on different types of animals (let’s say mammals, reptiles, and amphibians), the most common protocol would be to complete the lessons on mammals before moving to reptiles and completing the topic with amphibians. We generally refer to this as blocked learning, because we complete each block before moving to the next block (see fig. 1)

But what if I were to begin with an introductory lesson on mammals, but then move onto an introductory lesson on reptiles, then amphibians, before returning to mammals?

This second design is known as interleaving – we interleave distinct but related topics instead of blocking them together (see fig.2).

You might instinctively think that such a designs would have a detrimental impact on learning, after all, surely by the time you get around to mammals lesson 2, your learners will have forgotten most of what you taught them in mammals lesson 1?

However, this doesn’t appear to be the case. In studies, interleaving not only seems to speed up learning, it also might increase rates of transfer. 

In a study from 2008, Kornell and Bjork had participants learn the styles of twelve artists based on a sample of six paintings by each artist. In one condition, the artists’ paintings were interleaved among paintings by other artists. In the second condition, the artists were presented one after the other (blocked learning). 

After learning about the artists and their painting, the interleaved group were better able to identify the artist responsible for each of the series of new paintings. Interestingly, however, volunteers believed the blocking had been more successful. In other words, they displayed faulty metacognitive awareness. This isn’t unusual. A classic study into the spacing effect also resulted in participants believing that mass practice was better than spaced practice, a belief not supported by the evidence.

This curious finding might tell us a little more about illusionary performance. Blocking may well have helped the participants to notice commonalities, yet the final test required them to distinguish among the artists. Interleaving, on the other hand, may have fostered learning the differences as well as the similarities among the styles of difference artists. 

The case for interleaving is certainly strong, although in the short-term it might not appear to be effective. Why it’s better than blocked learning is a little more complicated. 

One explanation is that interleaving encourages learners to compare and contrast different types of related information. On Monday, our teacher introduces the class to mammals (warm-blooded, have hair or fur, give birth to live young), but on Tuesday students receive an introductory lesson on reptiles (cold blooded, lay eggs, have scales). This forces them to compare mammals with reptiles – mammals are warm-blooded, reptiles are cold-blooded.

This is why Zulkiply and Burt have dubbed interleaving the ‘compare and contrast effect’ (Zulkiply and Burt, 2013, p18). 

A second possibility is that interleaving forces learners to reload memories by introducing spacing. We know that some forgetting is beneficial for long-term learning because it requires more cognitive effort to recall it. Not only are students comparing and contrasting different types of animal, they are also revisiting information from previous lessons. 

When to use interleaving

Interleaving is beneficial to learning when items or topics are related. In the example above, mammals, reptiles, and amphibians are types of animal. We can compare and contrast them.

When not to use interleaving

Interleaving isn’t beneficial when the to-be-learned information is too different to allow learners to compare and contrast. If I were to teach a psychology class about different models of memory, they should benefit from interleaving because they could compare, say, the multi-store model of memory with the working memory model. However, interleaving memory models with lessons on social influence or explanations of conformity wouldn’t all for this.