Interleaving: Why Mixing Up Topics Beats Studying in Blocks

Studying one topic to exhaustion before moving on feels efficient, but mixing topics helps you learn more. Here's the science of interleaving.

Most students study in blocks: spend an hour on one topic, master it, then move to the next. It feels organised and efficient. But research on how we learn points to a counter-intuitive improvement, mixing topics together, a technique called interleaving.

What interleaving means

Interleaving means alternating between different topics or problem types within a study session, rather than doing all of one kind before moving on. Instead of twenty questions on topic A followed by twenty on topic B, you mix them: a bit of A, a bit of B, a bit of C, then back again. It feels harder and less smooth, and that difficulty is exactly why it works.

Why it works

When you study one topic in a block, each question feels easy because you already know which method to use, you just applied it to the last five. But an exam doesn't announce which topic a question belongs to. Interleaving forces you to first work out what kind of problem you're facing and then choose the right approach, which is the real skill you'll need. It also spaces your practice of each topic naturally, strengthening memory.

How to use it

• Mix related topics in one session rather than doing each to exhaustion.
• Shuffle your practice questions so consecutive ones come from different areas.
• Revisit earlier topics regularly instead of considering them 'done'.
• Expect it to feel harder, that's the sign it's working, not a problem.

The catch: it feels worse

Interleaving has a strange feature, it makes studying feel more difficult and your progress feel slower, even though you're actually learning more. Blocked practice feels smooth and confident but leads to weaker long-term retention. This gap between how learning feels and how effective it is trips up a lot of students, who abandon interleaving because it's uncomfortable. Trust the discomfort.

Combine it with testing

Interleaving is most powerful when the mixed practice is retrieval practice, questions you answer from memory rather than notes you re-read. A shuffled quiz that pulls from several topics at once trains you to identify and solve any kind of question, which is exactly what exam day demands.