Interleaving

interleaved practice, against blocked practice

Interleaving mixes problem types within one session instead of drilling one type at a time.

What it is

Practising one type of problem until it is smooth and then moving to the next is blocking. Shuffling the types so that the next question is unpredictable is interleaving.

The difference is not which problem you solve. Interleaving adds a step that blocking lets you skip: working out what kind of problem this is before solving it.

Why it feels worse

Blocked practice produces fast, visible improvement during the session — which is the easiest moment to measure and the least meaningful one. Interleaved practice feels jerkier and often scores lower while you are doing it.

The difference shows up later, on material you did not just practise, where the hard part is choosing a procedure rather than executing one.

How to use it

Once you recognise each type at all, stop running them in blocks and mix the ones you confuse with each other. Shuffled decks and mixed problem sets both count.

Keep the mixed set small enough to finish. Interleaving over a pile you never get through is procrastination with a theory attached.

Common mistakes

• Interleaving brand-new material. Mixing two types you cannot yet tell apart teaches you which one you do not understand — useful, but not yet the training.
• Judging a session by how smooth it felt. Smoothness inside a blocked session is mostly familiarity.
• Applying it to everything. A skill that must be fluent under time pressure still needs timed repetition.

Things you can try today

1. Do next week’s mixed homework in shuffled order, without looking up which chapter each question came from.
2. Before solving, say out loud which type the problem is and why. Naming is the step blocking never asks for.
3. Alternate two topics you confuse, ten minutes each, for a week, then retest yourself on the distinction.