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”
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.
See also
Mixing different kinds of problems in practice, interleaving, is a close cousin of spacing. It has its own page: Mix it up.
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 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
- 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. (accessed 2026-10-09)
- Ebbinghaus, H. (1885). Über das Gedächtnis: Untersuchungen zur experimentellen Psychologie. Duncker & Humblot (book; English: Memory, 1913). (accessed 2026-10-09)
- 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. (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)
- 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)
- Karpicke, J. D., & Roediger, H. L. (2008). The Critical Importance of Retrieval for Learning. Science, 319(5865), 966-968. (accessed 2026-10-09)
Related principles
Ready to learn
DuckyHelper is ready on your Mac. Learn with Eddy on its blackboard, or with Ducky right on your screen.
