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.