Interleaving

Mix different problem types in a session instead of doing them in blocks.

Why it works

Practicing one type of problem in a long block lets you reuse the same approach mechanically without choosing it, so you never learn which strategy fits which situation. Interleaving forces you to discriminate between problem types and retrieve the right approach each time, which is the skill you actually need when problems arrive unsorted in the real world.

How to do it

1. Mix related but different topics or problem types within a single study session.
2. Resist the urge to fully master one type before switching; switch while it still feels unsteady.
3. Practice identifying which kind of problem you face, not just executing a known procedure.

Evidence

Controlled studies, including in mathematics learning, find that interleaved practice produces better long-term performance and transfer than blocked practice, even though it feels harder and worse during practice. The benefit extends beyond procedures: Kornell & Bjork (2008) found interleaving also improved inductive learning of concepts and categories, even though learners wrongly believed blocking had helped them more. (rct)

Interleaving works best among related material where discrimination matters; mixing wholly unrelated topics, or interleaving before any basics exist, can be unhelpful.

Sources

• Rohrer & Taylor (2007), interleaved vs blocked mathematics practice, Instructional Science
• Rohrer, D., & Taylor, K. (2007). The shuffling of mathematics problems improves learning. Instructional Science, 35(6), 481–498.
• Rohrer, D., Dedrick, R. F., & Stershic, S. (2015). Interleaved practice improves mathematics learning. Journal of Educational Psychology, 107(3), 900–908.
• Kornell, N., & Bjork, R. A. (2008). Learning concepts and categories: Is spacing the 'enemy of induction'? Psychological Science, 19(6), 585–592.

Common mistake

Blocking practice by topic because it feels smoother and produces quick within-session gains, while undermining the durable, transferable learning that interleaving builds.