--- title: "Space it out: spaced practice and forgetting | DuckyHelper" url: "https://duckyhelper.com/research/principles/spaced-practice/" description: "The spacing effect and the forgetting curve: why reviewing after a gap beats cramming, what 317 experiments found, and how DuckyHelper schedules review." updated: "2026-10-09" --- Spaced practice # Space it out Reviewing something after a gap makes it last much longer than cramming it in one go. A review of 317 experiments (Cepeda et al., 2006) found spacing helps, and that the longer you need to remember, the longer the gap should be. DuckyHelper saves what you should keep as flashcards and brings each one back on a spaced schedule, right before you would likely forget it. > “the ISI producing maximal retention increased as retention interval increased” [Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin, 132(3), 354-380.](https://doi.org/10.1037/0033-2909.132.3.354) From Cepeda et al. (2006), Psychological Bulletin. ISI means the gap between study sessions. Reproduced for commentary. Source: [Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin, 132(3), 354-380.](https://doi.org/10.1037/0033-2909.132.3.354). In DuckyHelper ## Cards that come back on time In the film, the pill says it will quiz you again in three days, over Cepeda's highlighted line. What you save comes back on a schedule: - Flashcards on a real spaced schedule (Mac and web) - Mistakes become cards by themselves (Mac and web) - You see when it comes back (Mac app) - Reminded when cards are due (Mac and web) ## What the research found Hermann Ebbinghaus started this research in 1885 by memorizing lists of nonsense syllables and timing how fast he forgot them and how much faster he relearned them. The curve of forgetting he charted, steep at first and then flatter, is still the starting point. More than a century later, Nicholas Cepeda and colleagues pooled the experiments on spacing: > This review found 839 assessments of distributed practice in 317 experiments located in 184 articles. (Cepeda et al., 2006) Spacing beat massing, and the best gap grew with how long the memory had to last: to remember something for longer, leave longer gaps between reviews. A U.S. Department of Education practice guide (Pashler et al., 2007) made "Space learning over time" its first recommendation, and Dunlosky et al. (2013) rated distributed practice, with practice testing, as the most useful of ten study methods. Robert Bjork's idea of desirable difficulties explains the paradox: spacing feels harder, and that effort is part of why it lasts. ## Feature by feature ### Flashcards on a real spaced schedule Cards are scheduled with FSRS, an open spaced repetition algorithm. Each card's next review is set for when you are likely to still remember it about 90% of the time, and the gaps grow as you get it right. *Mac and web.* ### Mistakes become cards by themselves Missed quiz questions turn into flashcards, and the tutor saves a clean practice question for a kind of mistake it noticed (never your wrong work). *Mac and web.* ### You see when it comes back In the Mac app's review, each rating button shows when the card returns (Again, Hard, Good, Easy). *Mac app.* ### Reminded when cards are due When you have cards due, the tutor suggests a quick review near the start of the session. The Cards page shows what is due now and over the next 14 days. *Mac and web.* The missed question comes back as a real flashcard, with when each rating brings it back. From the film on forgetting: the missed one comes back as a flashcard, after longer and longer gaps. Click to watch the whole film: Ebbinghaus's forgetting curve, the testing effect and spaced review. See also Mixing different kinds of problems in practice, interleaving, is a close cousin of spacing. It has its own page: [Mix it up](https://duckyhelper.com/research/principles/interleaving/). 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 ### Distributed practice in verbal recall tasks: A review and quantitative synthesis Cepeda et al., 2006. Psychological Bulletin. Across 317 experiments, spacing helps, and longer retention calls for longer gaps. ### Über das Gedächtnis: Untersuchungen zur experimentellen Psychologie Ebbinghaus, 1885. Duncker & Humblot (book; English: Memory, 1913). First experiments on memory, charting the forgetting curve and effects of repetition. ### Organizing Instruction and Study to Improve Student Learning Pashler et al., 2007. IES Practice Guide (NCER 2007-2004), U.S. Department of Education. Seven research-based recommendations, including spacing, worked examples and quizzing. ### 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. ### 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. ### The Critical Importance of Retrieval for Learning Karpicke & Roediger, 2008. Science. Repeated testing, not repeated studying, drove long-term vocabulary recall. ## Frequently asked questions ### What is the spacing effect? Information is remembered better when study is spread out over time than when it is crammed into one session. It is one of the most replicated findings in memory research; Cepeda et al. (2006) reviewed 317 experiments. ### How long should I wait between reviews? It depends on how long you need to remember. Cepeda et al. (2006) found the best gap grows with the retention interval. Spaced repetition apps work this out per card from how well you recalled it. ### How does DuckyHelper decide when a flashcard comes back? It uses FSRS, an open spaced repetition scheduler, set to bring each card back when you would likely still recall it about 90% of the time. A missed card comes back in about ten minutes; a remembered one comes back days later. ## Sources 1. [Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin, 132(3), 354-380.](https://doi.org/10.1037/0033-2909.132.3.354) (accessed 2026-10-09) 2. [Ebbinghaus, H. (1885). Über das Gedächtnis: Untersuchungen zur experimentellen Psychologie. Duncker & Humblot (book; English: Memory, 1913).](https://archive.org/details/berdasgedchtnis00ebbigoog) (accessed 2026-10-09) 3. [Pashler, H., Bain, P. M., Bottge, B. A., Graesser, A., Koedinger, K., McDaniel, M., & Metcalfe, J. (2007). Organizing Instruction and Study to Improve Student Learning. IES Practice Guide (NCER 2007-2004), U.S. Department of Education.](https://ies.ed.gov/ncee/wwc/PracticeGuide/1) (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) 5. [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) 6. [Karpicke, J. D., & Roediger, H. L. (2008). The Critical Importance of Retrieval for Learning. Science, 319(5865), 966-968.](https://doi.org/10.1126/science.1152408) (accessed 2026-10-09) ## Related principles ### Explain it back in your own words: self-explanation The self-explanation effect: why students who explain ideas to themselves learn more (Chi et al.), the ICAP framework, and how DuckyHelper asks you to think. ### Feedback right away, on the step What research says about feedback: why it is powerful, why over a third of feedback studies found it hurt, and how DuckyHelper gives feedback on the step. ### 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. ## Keep reading ### 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. ### Mix it up: interleaved practice Interleaved practice in plain words: why mixing problem types helps learners tell them apart, what Rohrer and Taylor found, and what DuckyHelper does today. ### 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. ### It remembers how you learn and what you kept, so each lesson starts where you are; you hold the switches DuckyHelper remembers how you learn, what you studied and what you keep, so the next lesson starts where you are. You decide what it keeps and uses. ## 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.