Mix topics during retrieval practice rather than blocking by subject
When reviewing material from multiple topics, alternate between them rather than finishing one before moving to the next.
Why it works
Interleaving retrieval practice across topics forces the learner to identify which strategy or framework applies to each problem — a discrimination challenge that blocked practice avoids. This discrimination training builds a more flexible schema: you know not just how to solve a type of problem, but how to recognize which type of problem you’re facing. Short-term, interleaving feels harder and produces more errors; long-term, it produces substantially better transfer to novel problems.
How to do it
- When reviewing two or more topics, create a mixed question set rather than a topic-by-topic set.
- For each question, before answering, identify which topic or framework it belongs to — that identification is part of the learning.
- Accept that performance will be lower in interleaved practice than blocked; that difficulty is the mechanism, not a failure.
- Return to blocked practice only for material you haven’t yet grasped at all.
Evidence
Rohrer and Taylor (2007) and subsequent studies showed that interleaved mathematics practice produced better performance on delayed tests than blocked practice, even when blocked practice produced better scores on immediate tests. The "interleaving effect" has been replicated in motor learning and classification tasks. (rct)
Interleaving is most effective when the learner has some competence with each component skill; for complete novices on a topic, some blocked introduction may be needed before interleaving.
Sources
- Rohrer & Taylor (2007), The shuffling of mathematics problems improves learning, Instructional Science
Common mistake
Interpreting the lower performance during interleaved practice as evidence that it isn’t working, and switching back to blocked practice — which prevents the discrimination learning that interleaving builds.
Practice this with IX Coach
7 days free, then $40/month (~$1.30/day).
More practices for The Testing Effect: Why Retrieval Practice Beats Restudying
- Free recall immediately after a study session
Close all materials and write everything you remember from the session — without looking.
- Space retrieval attempts across increasing intervals
Test yourself on a topic after a delay, then again after a longer delay — the effort of retrieval at the edge of forgetting makes the memory strongest.
- Use frequent low-stakes quizzes rather than rare high-stakes tests
Regular short quizzes — even without grades — produce more retention than equivalent time spent reviewing.
- Ask "why is this true?" rather than just "what is this?"
Generate an explanation for why a fact or concept is true — the self-generated explanation is more memorable than the fact alone.
- Attempt to recall before studying new material
Try to answer questions about material before you’ve studied it — the attempt, even when wrong, enhances retention of the correct answer when it comes.
Related concepts
- Active Recall: The Most Effective Way to Study
The testing effect, retrieval practice, and how to build active recall into every session
- The Forgetting Curve: How Memory Decays and How to Fight It
Memory decay, the spacing effect, and how to schedule review so retention compounds rather than collapses
- The Worked Examples Effect: Learn Faster by Studying Solutions First
How to use solved examples, self-explanation, and fading to build skill faster than problem-first practice