Interleaving: why mixing topics can matter for learning
Interleaving: why mixing topics can matter for learning
Say you need to learn three topics: A, B, and C. You can practise them in blocks (AAAA, BBBB, CCCC) or mixed together (ABCABCABC). That second approach is called interleaving.
What is interleaving?
Interleaving means different topics, categories, or problem types are practised mixed together, instead of working through each topic fully before moving to the next. The idea is interesting because it forces the learner to keep deciding which knowledge or approach is needed here. That can be especially relevant when topics resemble each other.
An example
Say an employee needs to learn to recognise different safety situations. Practised in blocks, they get ten examples of type A, then ten of type B, then ten of type C, and always know which type is coming next during practice. Interleaved, the types are mixed (A, C, B, A, B, C), so the employee first has to work out what kind of situation this is, and only then which approach applies. That adds an extra decision moment that is closer to real practice.
Why can interleaving help?
A systematic review into interleaving in concept learning found evidence of benefits for both memory and transfer, especially when the differences between categories are subtle. Here too: interleaving is not a universal solution for every learning activity, context matters.
Interleaving versus spacing
These two concepts are often confused. Spacing is mainly about when you practise, interleaving is mainly about what you mix while practising. They can also be used together, for example by following order A, B, C in week 1, C, A, B in week 2, and B, C, A in week 4. Literature reviews highlight spacing and interleaving as related but distinct learning strategies.
Why can interleaving feel harder?
Practising in blocks often feels good: you practise the same skill repeatedly and notice yourself improving. Interleaving can feel harder, because you have to work out what to do each time. That can lead to lower performance during practice itself, while later learning or transfer can actually benefit. That is an important distinction: what feels easy during learning is not necessarily what works best later.
Say an employee needs to recognise different types of customer problems. You could give twenty questions about the same problem type in a row, but you could also mix different customer cases together. The employee then has to first recognise the problem, decide which knowledge is relevant, and pick the right approach. That is closer to reality: out in the field, nobody announces, this is now chapter 3, type B.
Interleaving in microlearning
You can apply interleaving quite simply, for example by only offering scenario A in week 1, scenario B in week 2, A and B mixed in week 3, and A, B, and C together in week 4. Later, the employee no longer gets a chapter order, but a realistic mix.
When should you not use it?
Interleaving can be awkward when someone still needs to build a completely new basic skill. A beginner sometimes needs clear, guided instruction first, after which you can gradually introduce more variation. A practical order is: explanation, guided practice, blocks, mixing, and only then application, not everything mixed together from minute one.
Interleaving and Stiqqo
For a retention programme, interleaving becomes interesting once there is enough content. Instead of dedicating week 1 and 2 fully to topic A and only starting topic B in week 3, you can combine different core topics once the basics are in place. The employee then has to not just remember, but also select, and that is exactly what happens in many real-world situations.
Conclusion
Interleaving isn't simply about 'making the training more varied'. It is about deliberately mixing different concepts, problem types, or skills during practice. It can be especially useful when employees later need to independently recognise which knowledge or approach fits a situation, making it an interesting complement to spacing and retrieval practice.