Dempster, F. N. (1988). A Case Study in the Failure to Apply the Results of Psychological Research. American Psychologist, 43(8), 627–634

One important possible objection: classrooms often do little repeated presentation of any kind—they’re just zipping through material. And so the difference between spacing and massing doesn’t matter much.

For one month recall, the impact of the spacing effect is huge, but for shorter test intervals, it’s much smaller. (but contradicted by Dempster 1987b)

Massed practice feels like it’s working.

The high order bit for teachers is not that struggling students are learning things, and then forgetting—but rather that they’re never learning things in the first place. That is, classrooms don’t do “repeat until successful” in the way that Ebbinghaus does. i.e.:

With respect to the latter, it may be that under certain lengthy lag conditions, the usual benefits of spaced repetitions do not obtain because theresults of initial processing efforts have been forgotten

It is used, for things like the alphabet, and for reading, and for basic arithemetic—just implicitly. Teachers will have their kids sing the alphabet every day of the year.

With respect to the educational implications of their study, the authors concluded that long-term retention would almost certainly be enhanced if foreign language courses make certain that students independently retrieve target information at intervals that are as long as 1 month, over a period of several years, instead of the more typical intervals of 1 to 2 days over periods of from 10 to 15 weeks.

And how exactly is a teacher supposed to make that happen, given the structure of a semester?

Possible claim: most classroom time is devoted to the presentation of new material, rather than the review or practice of old material.

Claim: to the extent that classroom review and practice happen, spaced presentation is already happening to a large extent—implicitly or explicitly—and further spacing is unlikely to help.

Cepeda (2008) offers a good explanation:

If a person wishes to retain information for several years, a delayed review of at least several months seems likely to produce a highly favorable return on the time investment— potentially doubling the amount ultimately remembered com- pared with a less temporally distributed study schedule, with study time equated.

David Robson (Spiral Math) suggests that cultural issues are the main blocker.

• he contrasts the flight instruction setting from the classroom
• K-12 culture does not reward retention
• zero-sum classroom practitioners
• “third graders have it harder than college students, because we expect them to remember all the third grade material and bring it into the fourth, whereas with college students, most topics won’t be ever revisited in a four year span”
• amateur pilots must do 3 takeoffs in 90 days to bring someone else along!
• we have higher expectations now that “everybody becomes college-ready”, which creates additional pressures

Maria Droujkova: “in mathematics, you just need to have ‘happy familiarity’; whereas in language learning, you need something more durable.” Supports more light exposure.

Andrew Sutherland suggests: it’s a tooling issue; teachers will need support.