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Study Methods

Interleaving: Mix Problem Types While You Practice

Moderate or mixed evidence 5 min read Level: Intermediate Reviewed October 30, 2026

Interleaving means mixing different problem types in one study session. Learn how it works, with math examples, and where the research is limited.

Evidence rating: Moderate or mixed evidence. Mixing problem types in one session has beaten practicing one type at a time in several studies, mostly in math and in learning to tell categories apart (Rohrer & Taylor, 2007; Rohrer et al., 2020). A large review rated it as promising but noted limited testing in real classes (Dunlosky et al., 2013). Results are less clear for some kinds of material, such as when the items are very different from each other or when students are brand new to a topic. How we rate evidence

What it is

Interleaving means mixing different kinds of problems or topics in one study session, instead of finishing all of one kind before moving on. The usual way, called blocked practice, looks like this: ten problems on one skill, then ten on the next. Interleaved practice shuffles them: A, C, B, A, B, C.

Blocked practice feels smooth. After the first two problems you know which method to use, so you stop thinking about the choice. On a real test the problems come mixed, and the first job is to decide which method fits. Interleaving practices that job.

In one well-known study, students learned to find the volume of four solid shapes. Some practiced one shape at a time and some practiced them mixed. A week later the mixed group scored much higher on a test (Rohrer & Taylor, 2007). A later classroom trial with seventh graders also found an advantage for mixed practice on a delayed test (Rohrer et al., 2020). Keep in mind that interleaving is about similar items. Mixing algebra with art history will not teach you to choose between methods. The gain seems to come from putting side by side the things you tend to confuse, so you notice what makes each one different. A good rule is to start with two or three related skills and add more only after the mix feels manageable. Mixing also spaces out each skill, because you come back to it after other work. That may be part of the reason it helps.

When to use it

  • You have already learned two or more similar skills, such as different types of equations, and tend to mix them up.
  • Your homework is one skill at a time, but your exams mix everything.
  • You are learning to tell categories apart, such as types of chemical reactions, painting styles or verb tenses.
  • You have several days before the test and can practice a little each day.

How to apply it

  1. First learn each skill on its own until you can do a few problems with help. Interleaving is for practice, not for the first lesson.
  2. List the skills or topics you need to practice. Three or four is a good start.
  3. Collect a few problems for each one from homework, the textbook or old quizzes.
  4. Shuffle them. Write each on a card or number them and use a random order.
  5. Before solving each problem, write down which type it is and why. Then solve it.
  6. Check your answers. Keep a note of the problems where you picked the wrong method.
  7. Repeat on later days with a new mix, and add earlier topics so older skills stay fresh.

Step-by-step examples

Example: math review with three equation types

  1. Your unit covers linear equations, quadratic equations and systems of equations.
  2. Take four problems of each type from the textbook, 12 in total, and shuffle them.
  3. For each one, write a few words: 'quadratic, has x squared, try factoring.'
  4. Solve, then check the answer key. Suppose you treated two quadratics like linear ones.
  5. Next day, make a new set that includes the types you mixed up, plus a few from last week.

Example: telling apart three kinds of chemical reactions

  1. Write 12 short reaction examples on cards: synthesis, decomposition and single replacement, four each.
  2. Shuffle the cards and look at the first one without the label.
  3. Say the type out loud and give one clue that tells you, such as 'one compound breaks into two.'
  4. Turn the card to check. Put wrong ones in a separate pile.
  5. Go through the wrong pile again after the other cards, then repeat the next day.

Advantages

  • It trains you to choose the right method, which is what mixed tests ask for.
  • It can help you tell similar ideas apart.
  • Each skill gets revisited, which builds in some spacing.
  • It needs no extra materials, only a way to shuffle the problems you already have.

Limitations

  • It feels harder and your scores during practice may look worse. That can make it seem like it does not work.
  • Most evidence comes from math and category learning. Evidence for other subjects is thinner.
  • It is not meant for the first time you meet a skill. You need a base before mixing.
  • Gains in studies were often measured on a test a week or so later. Effects for a quiz tomorrow may differ.

Common mistakes

  • Mixing before you understand any one skill, which only creates confusion.
  • Mixing topics that have nothing in common, such as unrelated chapters, when the benefit comes from similar items.
  • Not naming the problem type before solving it.
  • Quitting because scores drop in the first session.
  • Never going back to blocked practice when a skill is shaky and needs focused work.

Recommended next steps

Part of the path Prepare for Exams (step 3 of 6). Next in this path: Error Log Method: Turn Mistakes Into a Study List.

References

  1. Rohrer, D., & Taylor, K. (2007). The shuffling of mathematics problems improves learning. Instructional Science, 35(6), 481-498.
  2. Rohrer, D., Dedrick, R. F., Hartwig, M. K., & Cheung, C.-N. (2020). A randomized controlled trial of interleaved mathematics practice. Journal of Educational Psychology, 112(1), 40-52.
  3. Kornell, N., & Bjork, R. A. (2008). Learning concepts and categories: Is spacing the 'enemy of induction'? Psychological Science, 19(6), 585-592.
  4. Dunlosky, J., Rawson, K. A., Marsh, E. J., Nathan, M. J., & Willingham, D. T. (2013). Improving students' learning with effective learning techniques: Promising directions from cognitive and educational psychology. Psychological Science in the Public Interest, 14(1), 4-58.

This guide is general educational information. Study methods work differently for different people, and no method guarantees better grades or results.

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