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.”
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
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
- Rohrer, D., & Taylor, K. (2007). The shuffling of mathematics problems improves learning. Instructional Science, 35(6), 481-498. (accessed 2026-10-09)
- Kornell, N., & Bjork, R. A. (2008). Learning Concepts and Categories: Is Spacing the “Enemy of Induction”? Psychological Science, 19(6), 585-592. (accessed 2026-10-09)
- Bjork, R. A. (1994). Memory and Metamemory Considerations in the Training of Human Beings. Metacognition: Knowing about Knowing (MIT Press, book chapter). (accessed 2026-10-09)
- 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. (accessed 2026-10-09)
Related principles
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