Heuristic
Interleave only where choosing matters
Mixing is a design choice, not a ritual.
When it fits
- When a study plan mixes topics simply because interleaving is supposed to be superior.
When to avoid it
- Some materials in the meta-analysis showed little benefit or an advantage for blocking. Treat interleaving as conditional.
Why it matters
Ask whether the real task requires selecting among similar methods or categories. If yes, mix those cases so the learner must choose. If the material is still being introduced or categories are not meaningfully confusable, blocked work may be clearer. Reassess from performance rather than ideology.
An example
Mixing several similar chart-selection problems can train choice; alternating an unrelated language drill, coding task and accounting chapter may add switching without a useful discrimination problem.
Check your result
The reason for interleaving names a target decision that mixed practice is supposed to improve.
Keep this limit in mind
- Some materials in the meta-analysis showed little benefit or an advantage for blocking. Treat interleaving as conditional.
Evidence and sources
A meta-analysis of interleaving found a moderate overall benefit (g = 0.42) but strong moderation by material type and category similarity, including conditions where blocking performed better.
Interleaving should be selected for a discrimination problem rather than used as a universal mixing rule.
Similarity matters: A meta-analysis of interleaved learning and its moderators · Abstract