--- title: "Mix it up: interleaved practice | DuckyHelper" url: "https://duckyhelper.com/research/principles/interleaving/" description: "Interleaved practice in plain words: why mixing problem types helps learners tell them apart, what Rohrer and Taylor found, and what DuckyHelper does today." updated: "2026-10-09" --- Interleaving # Mix it up Interleaving means mixing different kinds of problems in one practice session instead of doing a block of one kind, then a block of the next. In Rohrer and Taylor (2007), students who practiced math problems mixed did far better on a test a week later. DuckyHelper's flashcard reviews mix due cards from every topic, and you can ask for a mixed quiz at any time. > “When tested 1 week later, performance was vastly superior after mixed practice.” [Rohrer, D., & Taylor, K. (2007). The shuffling of mathematics problems improves learning. Instructional Science, 35(6), 481-498.](https://doi.org/10.1007/s11251-007-9015-8) From Rohrer and Taylor (2007), Instructional Science. Reproduced for commentary. Source: [Rohrer, D., & Taylor, K. (2007). The shuffling of mathematics problems improves learning. Instructional Science, 35(6), 481-498.](https://doi.org/10.1007/s11251-007-9015-8). In DuckyHelper ## Reviews that mix your topics In the film, a missed question comes back later as a flashcard. DuckyHelper does not build mixed problem sets on its own yet. Two things already mix your practice: - Reviews mix your topics (Mac and web) - Ask for a mixed quiz (Mac and web) ## What the research found Most textbooks group practice by topic: twenty problems on one kind, then twenty on the next. Doug Rohrer and Kelli Taylor shuffled them instead. In their second experiment, practice was either blocked by type or mixed. A week later, the mixed group did far better on the test (the line quoted at the top of this page). Mixing helps for a simple reason: on a test you first have to recognize *what kind* of problem it is. Blocked practice tells you the answer to that question; mixed practice makes you work it out. Nate Kornell and Robert Bjork found the same with art. People studied paintings by different artists, grouped by artist or mixed, then had to name the artist of new paintings: > Surprisingly, induction profited from spacing, even though massing apparently created a sense of fluent learning (Kornell & Bjork, 2008) That last part matters: mixing usually *feels* worse while helping more, which is one of Bjork's desirable difficulties. The evidence is younger than for spacing or testing, and Dunlosky et al. (2013) were careful: > Elaborative interrogation, self-explanation, and interleaved practice received moderate utility assessments. (Dunlosky et al., 2013) ## Feature by feature ### Reviews mix your topics A flashcard review started without picking a deck pulls every card that is due, from every topic, most overdue first, so one review mixes subjects. *Mac and web.* ### Ask for a mixed quiz Quizzes are written for you on the spot, so you can ask for a mix: "quiz me on fractions, decimals and percents, mixed up." Quizzes can mix question types too. *Mac and web.* Being honest about it DuckyHelper does not yet plan interleaved practice sets on its own. Today the mixing comes from reviews across decks and from what you ask for. What this page does not claim These studies tested other people, other schools and other tools. DuckyHelper has not been tested in a study like these, so none of these results are DuckyHelper's results. They are the reasons behind how it teaches. ## The papers on this page ### The shuffling of mathematics problems improves learning Rohrer & Taylor, 2007. Instructional Science. Mixing different problem types in practice improved later math test scores. ### Learning Concepts and Categories: Is Spacing the “Enemy of Induction”? Kornell & Bjork, 2008. Psychological Science. Interleaving artists' paintings improved learning each style, though massing felt better. ### Memory and Metamemory Considerations in the Training of Human Beings Bjork, 1994. Metacognition: Knowing about Knowing (MIT Press, book chapter). Conditions that make practice harder can make learning last longer. ### Improving Students’ Learning With Effective Learning Techniques: Promising Directions From Cognitive and Educational Psychology Dunlosky, Rawson, Marsh, Nathan & Willingham, 2013. Psychological Science in the Public Interest. Of ten study techniques, practice testing and spacing were rated most useful. ## Frequently asked questions ### What is interleaved practice? Mixing different kinds of problems or topics within one practice session, instead of finishing one kind before starting the next. It trains you to recognize which method a problem needs. ### Is interleaving better than blocked practice? On later tests it often is. In Rohrer and Taylor (2007), mixed math practice gave much better results a week later. Reviews rate the evidence as moderate so far, and mixing usually feels harder while you do it. ### Does DuckyHelper interleave practice automatically? Partly. A flashcard review without a chosen deck mixes due cards from every topic. It does not yet build interleaved problem sets by itself, but you can ask for a mixed quiz any time. ## Sources 1. [Rohrer, D., & Taylor, K. (2007). The shuffling of mathematics problems improves learning. Instructional Science, 35(6), 481-498.](https://doi.org/10.1007/s11251-007-9015-8) (accessed 2026-10-09) 2. [Kornell, N., & Bjork, R. A. (2008). Learning Concepts and Categories: Is Spacing the “Enemy of Induction”? Psychological Science, 19(6), 585-592.](https://doi.org/10.1111/j.1467-9280.2008.02127.x) (accessed 2026-10-09) 3. [Bjork, R. A. (1994). Memory and Metamemory Considerations in the Training of Human Beings. Metacognition: Knowing about Knowing (MIT Press, book chapter).](https://doi.org/10.7551/mitpress/4561.003.0011) (accessed 2026-10-09) 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.](https://doi.org/10.1177/1529100612453266) (accessed 2026-10-09) ## Related principles ### Teach one on one: the 2 sigma problem Bloom's 2 sigma problem in plain words: what one-on-one tutoring did in the studies, what later reviews found, and how DuckyHelper tutors. ### Guide, don't hand over answers A 2025 PNAS study found that unguarded GPT-4 help raised practice grades but lowered exam grades. What it means, and how DuckyHelper guides instead. ### Show a worked example first The worked example effect: why studying solved problems helps beginners more than solving alone, when it stops helping, and how DuckyHelper shows steps. ## Keep reading ### Space it out: spaced practice and forgetting The spacing effect and the forgetting curve: why reviewing after a gap beats cramming, what 317 experiments found, and how DuckyHelper schedules review. ### Quiz, don't re-read: retrieval practice The testing effect: why pulling an idea out of memory beats re-reading it, with the real numbers from Roediger and Karpicke, and how DuckyHelper quizzes you. ### Keep the learner doing, not watching: active learning Active learning in plain words: the 225-study PNAS meta-analysis, why active classes feel like less learning, and how DuckyHelper keeps you doing. ### The learning-science library: 100+ papers 100+ real learning-science papers behind DuckyHelper, sorted by principle, each with a citation, a link to the publisher and a one-line summary. ### Cards made from your lessons and mistakes, back right before you would forget them DuckyHelper turns your lessons and your mistakes into flashcards that come back right before you would forget them. Review with Eddy or in the Mac pill. ### Say quiz me: tap, type math or answer true or false, and every miss comes with why Say quiz me and DuckyHelper writes a quick quiz on what you are learning: tap, type math or answer true or false, and every miss comes with why. ## Ready to learn DuckyHelper is ready on your Mac. Learn with Eddy on its blackboard, or with Ducky right on your screen. [Download for Mac](https://duckyhelper.com/download/) [See what it does](https://duckyhelper.com/features/) The Mac app needs Apple silicon and macOS 14 Sonoma or later. There is no Chromebook, Windows or web version right now.