Interleaved practice: why mixing topics helps you learn

In one study, college students learned to calculate the volumes of different solids. Students who practised with problems mixed together performed much better on a test a week later than students who practised each type in a block, even though the blocked group did better during practice itself (Rohrer and Taylor, 2007).

Interleaving has also helped in other kinds of learning. In a study where people learned to recognise painters' styles, seeing paintings by different artists mixed together led to better recognition of new paintings than seeing each artist's paintings in a block (Kornell and Bjork, 2008).

• Choosing the method. Interleaving forces you to identify what kind of problem you're facing, which is exactly what tests require.
• Noticing differences. Seeing different problem types side by side highlights what makes each one different.
• Built-in spacing. Mixing topics naturally spreads out practice on each one, which also helps memory. See spaced repetition.

Blocked set (all the same type):

1. Solve $3x + 4 = 19$
2. Solve $5x - 2 = 18$
3. Solve $2x + 7 = 15$

Interleaved set (mixed types):

1. Solve $3x + 4 = 19$
2. Find the area of a circle with radius 5 cm
3. Increase 80 by 15%
4. Solve $x^2 - 9 = 0$
5. Simplify $\tfrac{12}{18}$

In the interleaved set, every question starts with a decision: what kind of problem is this, and which method fits?

1. Learn something new with a short block. When a method is brand new, a few examples in a row help you understand it.
2. Then mix it in. Once you can do it, practise it alongside earlier topics.
3. Build mixed sets for revision. Take questions from several chapters, shuffle them, and work through them.
4. Use past papers. Exam papers are naturally interleaved.
5. Expect it to feel harder. Making more mistakes during mixed practice is normal; it's a sign you're learning the decision, not just the steps.

The strongest evidence is in maths and for learning to tell similar categories apart. Interleaving is most useful when topics are related enough to be confused with each other (different types of equations, similar historical causes, different chemical reactions). Mixing completely unrelated subjects in one session doesn't give the same benefit. Researchers also note that the evidence base is still growing, so combine interleaving with the best-established techniques: active recall and spacing.

Building good mixed sets takes effort. An AI tutor can do it for you: ask TutorAura for "ten mixed questions on this term's algebra and geometry", and it checks your working, so you find out straight away whether you chose the right method. See also how to revise for GCSE Maths and how to study math.