Practising one type of problem over and over until you've "got it," then moving to the next type, feels like the obvious way to study. It is also, for long-term learning, one of the worst. A counterintuitive technique called interleaving consistently beats it — even though it feels harder while you do it.

Blocked vs. interleaved practice

Blocked practice means doing all of topic A, then all of B, then all of C (AAA BBB CCC). Interleavedpractice mixes them up (ABC BCA CAB). The total amount of practice is identical; only the order changes.

Several open books spread across a desk at once
Interleaving mixes topics instead of massing them. Switching between them forces you to choose the right method each time — exactly what an exam demands (Rohrer & Taylor, 2007).

In a well-known 2007 experiment, Doug Rohrer and Kelli Taylor had students learn to calculate the volumes of different solids. The blocked group crushed the practice session. But on a test a day later, the interleavedgroup more than doubled them. The group that struggled more during practice learned far more.

Why mixing it up works

  • It forces you to choose a strategy. In blocked practice you already know every question needs the same method. In real exams — and in interleaved practice — you first have to figure out which method applies. That discrimination skill is most of the battle.
  • It builds in spacing. Returning to a topic after doing others is a mini spaced review, which strengthens memory on its own.
  • It exposes shallow understanding. Blocked practice lets you run on autopilot. Mixing problems reveals what you only thought you understood.
Interleaving feels worse and works better. The desirable difficulty you experience during practice is exactly what makes the knowledge stick.

Watch out for the feeling

The hardest thing about interleaving is psychological. Blocked practice produces a smooth sense of fluency that feels like learning. Interleaving feels bumpy and slow. Students consistently rate blocked practice as more effective — and consistently learn more from interleaving. Don't trust the feeling; trust the test.

Key takeaways

  • Interleaving (mixing topics) beats blocking (one at a time) on later tests.
  • It works because exams require choosing the right method, not just applying one.
  • Mixing builds in spacing and exposes shallow understanding.
  • It feels harder and less effective — that feeling is misleading.

How DoubtGo mixes your practice for you

Left to our own devices, most of us default to comfortable blocked practice. DoubtGo's quizzes and review sessions deliberately mix topics and problem types from across your study sets, so you build the discrimination skills an exam actually tests. Combine that with spaced repetition and you're training the way the research says works best. Try it free.