interleaving: the mix-it-up memory method that works

fluency is a bad teacher - what feels good misleads learners about what they've learned

Want to strengthen your learning and memory? Read on…

Continuing this series on experimentally-tested, effective, empirically-demonstrated, and theoretically-founded methods of enhancing learning and memory.

When you go to the gym, you expect gains entail (a little) pain, or effort, exertion, and discomfort.

Learning demands the same!

(PS: coming soon, why learning styles do not exist, so you can save yourself the trouble of thinking about them ever again… and further posts on action-oriented learning, applying optimal strategies from learning science to sport, music and other domains where expert knowledge is vital.)

interleaving: the mix-it-up memory method that works

what is interleaving?

Interleaving means rotating across related topics, concepts, or problem types within the same study block.

Suppose you're doing some difficult geometry problems: instead of finishing all the sphere problems and only then moving to cubes, you purposely alternate: sphere; cube; pyramid; back to sphere; and so on.

Blocking means practising one topic or skill at a time - something students tend to do - concentrating on one thing at a time. Interleaving mixes related topics within the same session—for example, instead of AAA–BBB–CCC you instead rotate between items as follows: ABC–ABC–ABC. Across many studies, interleaving tends to produce better long-term retention and method selection than blocked practice, especially when you must distinguish between similar problems, even though blocking often feels easier during study.

To push the gym analogy a bit: block training is like doing all your bench-press sets, then all your squats, then all your rowing: AAA, BBB, CCC.

Interleaving is circuit training: bench, squat, row; repeat: ABC, ABC, ABC. The circuit feels tougher, because you must reset grip, stance, and breathing each time; switching teaches you to choose the right movement under pressure and builds more durable, transferable form.

Blocked sessions feel smoother in the moment, but mixed sessions pay off when it’s time to perform.

Similarly, each topic switch forces you to decide what kind of thing you’re facing and which method fits. Repeatedly having to pay attention to differences (shape, sizes, angles, spatial relationships) trains discrimination: you get better at spotting ‘what it is’, before ‘learning how to do it.’

Because each topic is revisited after a gap, you also get built-in spacing; pulling the right rule back from memory strengthens it remember the discussion of retrieval practice; link below). The learning and practice session feels less smooth than blocked practice, but the learning is more durable.

The challenge for the learner is mostly cognitive and metacognitive. Cognitively, these switches create interference: your working memory must drop one procedure and load another; decision time increases; mistakes rise at first.

You can’t rely on the last problem’s pattern; you must choose afresh, which is effortful. Metacognitively, interleaving feels like worse performance, because it’s slower, less fluent, and prone to more errors: your intuition says it isn’t working.

But your intuition is wrong.

Blocked practice - sticking to the one topic for long periods of time -by contrast, feels easy and rewarding in the moment because you are exercising the same rules again and again; it inflates confidence without building flexible knowledge.

using your memory to strengthen your memory: retrieval practice

implementing interleaving to enhance learning and memory

(btl: why interleaving works; interleaving and retrieval practice reinforce each other; when to interleave (and when not to); how much to switch; designing interleaved sets; common pitfalls; a practical protocol for interleaving; protocol card: “interleave + retrieve”; readings)