Blocked vs interleaved practice
Blocked practice drills one skill repeatedly before moving on: AAAA, BBBB, CCCC. Interleaved practice mixes them: ABCABCABC. Same problems, same time — only the order changes.
In study after study, learners who interleave do worse during practice but substantially better on a later test. The mixing is what makes it transfer.
Why it feels worse but works better
Blocking feels smooth because once you know you're doing derivatives, you stop deciding which method to use — you just apply it. That's the catch: on a real exam, nobody tells you which method a problem needs.
Interleaving forces you to first identify what kind of problem you're facing, then solve it. That discrimination step is exactly the skill exams test, and blocked practice quietly skips it.
What it's good for
Interleaving shines when topics are similar and easy to confuse — problem types in math and physics, similar vocabulary, look-alike concepts, categories that share features.
It matters less for a single isolated skill with no near-neighbors to confuse it with. The benefit comes from learning to tell related things apart.
How to interleave
It's mostly about ordering, not extra work:
- Mix topics in one review session instead of one topic per day.
- Shuffle problem sets so consecutive problems need different methods.
- Study several related decks together rather than finishing one before starting another — a spaced-repetition app naturally interleaves due cards across decks.