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When to Block vs When to Interleave: The Conditional Rule

A pragmatic rule for doctors: block to build the schema, interleave to train discrimination.

Review date
Feb 2026
Reading time
8 min read
Author
Dr. Kola Tytler MBBS CertHE MBA MSt MRCGP
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Key points

  • Block early when you’re building basic schema (novice phase).
  • Interleave once you can answer ‘easy versions’ reliably.
  • Use interleaving to train discrimination under time pressure.

Your signal that it’s time to interleave

If you’re getting most ‘single-topic’ questions right but still fail when options are mixed, you need discrimination training—interleaving is the tool.
Blocking can feel productive because performance rises quickly. Interleaving can feel like you’re regressing. In reality, they train different things. Exams reward the ability to choose between plausible alternatives under time pressure—interleaving is built for that.
1

Phase 1 (Block): build the map

Do focused blocks to understand the condition, typical presentation, and management pathway.
2

Gate condition

When you can answer ‘straightforward’ questions reliably, stop blocking. The returns drop fast.
3

Phase 2 (Interleave): train the choice

Create near-neighbour sets and mix questions. Track discriminators, not scores.
4

Phase 3: escalate realism

Increase time pressure, ambiguity, and mixed topics once discrimination is improving.

My block vs interleave decision

  • If I’m a novice: block.
  • If I’m failing on confusables: interleave.
  • If I’m tired: Tier 1 maintenance only.
  • If I interleave: I write discriminators.
  • I always schedule a retest block.
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Study methods · Article 30 of 48