09/30/2024

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tl;dr - I founded a nonprofit (www.podsie.org) that's trying to make spaced repetition a lot more accessible for teachers and students in K-12 classrooms. We're hiring for a senior dev, and by telling you more about the research behind our work, along with our progress so far, I’m hoping to convince you to apply for the role!

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Spaced repetition is a learning method based on computing optimum intervals that should separate review of individual pieces of knowledge to achieve a desired level of retention.

The above definition is from Piotr Wozniak, a researcher credited with creating the first computer-based spaced repetition system. Put more simply, spaced repetition is an effective way of learning where you space out your practice of content over time. Despite its name, spaced repetition isn't about rote memorization, but rather about strategically timed review to enhance understanding and retention. If you've ever used Duolingo, you've likely experienced spaced repetition before whenever you practiced a vocab word on day 1 and then reviewed that same word again a few days later. It's research-backed, and generally, it's very effective in helping learners retain information over long periods.

Wozniak also states definitively:

Spaced repetition does not work in a classroom

Specifically, he believes that spaced repetition is inherently a personal tool that conflicts with the rigidity of traditional school settings.

I disagree! My differing opinion stems from work that I’ve done over the past four years, which includes:

• digging deeply into the research behind spaced repetition
• building a proof-of-concept web app that helps teachers use spaced repetition with their students (and has reached ~2k teachers and ~20k students)
• working closely with learning scientists from Carnegie Mellon and The University of Memphis on a National Science Foundation-funded research project on spaced repetition

Overall, I strongly believe that, if implemented thoughtfully, spaced repetition can meaningfully improve learning outcomes in every K-12 classroom in the US.

The research behind spaced repetition

Fundamentally, spaced repetition is grounded in two of the most robustly supported learning strategies in cognitive science: the spacing effect and retrieval practice.

Spacing

The spacing effect refers to the phenomenon where learning is more effective when study sessions are spread out over time, rather than concentrated in a single session. Those one-time last-minute cram sessions just don’t work as well.

Over 35 years ago, Frank N. Dempster, a cognitive science researcher wrote:

The spacing effect--which refers to the finding that for a given amount of study time, spaced presentations yield substantially better learning than do massed presentations --is one of the most remarkable phenomena to emerge from laboratory research on learning. It is remarkable in several respects. First, the spacing effect is one of the most dependable and replicable phenomena in experimental psychology. Second, it is remarkably robust. In many cases, two spaced presentations are about twice as effective as two massed presentations (e.g., Hintzman, 1974; Melton, 1970), and the difference between them increases as the frequency of repetition increases (Underwood, 1970). Moreover, demonstrations of achievement following massed presentations often are only slightly higher than that following a single presentation (e.g., Melton, 1970). Third, the spacing effect is truly ubiquitous in scope. It has been observed in virtually every standard experimental learning paradigm, with all sorts of traditional research material (Dempster, 1987a; Hintzman, 1974; Melton, 1970).