Interleaving: why mixing topics beats studying them in blocks

Interleaving is the practice of mixing several topics or problem types within a single study session, rather than finishing all of one kind before moving to the next (which is called blocking). It feels less smooth than blocked practice, but research shows it leads to better learning and transfer — especially for problem-solving.

The short version

Interleaving mixes topics; blocking does one at a time.
Interleaving feels harder but improves later performance and transfer.
It's most useful when problem types are easy to confuse.
Mixing decks or subjects in a session interleaves your flashcards.

Blocked vs interleaved practice

Blocked practice does all of topic A, then all of topic B, then all of topic C. Interleaved practice mixes them: a bit of A, then C, then B, then A again. Blocking feels easier and more organized; interleaving feels messier and more effortful.

That extra effort is the point. When problems are mixed, you can't run on autopilot — you have to first figure out which kind of problem you're facing, which is the skill you actually need later.

When interleaving helps most

Interleaving is especially valuable when topics are easy to confuse, or when you need to choose the right method for a problem — math, science, languages, classification tasks. Studies (notably on math practice) find that students who interleave often perform worse during practice but markedly better on later tests than those who block.

With flashcards, interleaving happens naturally when you mix decks or subjects in a session rather than drilling one deck to exhaustion.

Frequently asked

What is interleaving in studying?

It's mixing different topics or problem types within one study session, instead of completing all of one type before starting the next.

Why is interleaving better than blocking?

Mixing forces you to identify what kind of problem you're facing and choose the right approach — the exact skill you need on a test. Blocked practice lets you coast, so it looks better during study but transfers worse.

Doesn't interleaving make studying feel worse?

Often, yes — performance during practice can dip, which is why many learners avoid it. But that difficulty is productive: interleaved learners tend to do better when it counts.

How do I interleave with flashcards?

Study a mix of decks or subjects in the same session rather than drilling a single deck start to finish. Koydo's daily reviews naturally blend cards across what you're learning.

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