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Interleaving

Mixing different topics or problem types in one session, instead of drilling one at a time.

What it is

  • Blocking: practice A-A-A-A, then B-B-B-B, then C-C-C-C.
  • Interleaving: practice A-C-B-A-B-C — shuffled.

Why it works

Interleaving feels worse and produces worse performance during practice — but markedly better retention and transfer to new problems later. The classic study (Rohrer & Taylor): students who interleaved math problem types scored 63% on a delayed test vs 20% for blocked practice — even though blocked practice looked better during training.

Why? Blocking lets you autopilot ("they're all type A, so apply the type-A method"). Interleaving forces you to first figure out which kind of problem you're facing — the exact discrimination skill you need in the real world, where problems don't come pre-labeled.

Block first, then interleave

There's a sequence. When a topic is brand new, a little blocked practice helps you build the basic pattern. Once you've got the basics, switch to interleaving to make it durable and flexible. Acquire blocked → retain interleaved.

How to use it

  • Don't do 50 of the same problem type in a row. After you've grasped it, mix it with related types.
  • Practice discrimination: deliberately put similar-but-different cases side by side so you learn to tell them apart.
  • Expect it to feel harder and messier than blocking. That's the desirable difficulty doing its job.

Try this

In your next practice session, after warming up on a new pattern, shuffle it together with 2–3 related ones you already know. Force yourself to identify the situation before choosing the response.

In poker

Drill random spots (GTO Wizard Full Hand mode) across formations rather than grinding one node 200× — random spots force you to first identify which situation you're in. Block a new spot to learn it, then interleave. → Drilling Spots

Key takeaway

Mix it up. Blocked practice builds confidence; interleaved practice builds the skill you can actually use when situations come at you in random order.

Sources: Rohrer & Taylor, via Bjork & Bjork · Kornell & Bjork (2008)