michael_nielsen on Twitter: "Of course, "everyone who sticks with it" is a significant caveat. Maybe people who aren't going so well give up? We're investigating whether that might be the case or not."

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michael_nielsen‏ @michael_nielsen Jun 26

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That's pretty good, I think. If you're anything like me, a few weeks after reading something you have only a hazy memory. By contrast, these people have, at very low cost (of which more below), got a month or so of demonstrated retention across more than 100 detailed questions

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michael_nielsen‏ @michael_nielsen Jun 26

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This is the big hoped-for advantage of spaced repetition, and what makes it counterintuitive and unusual: you get _exponential returns_ for increased effort.

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michael_nielsen‏ @michael_nielsen Jun 26

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It typically takes about 80 minutes of review time to get to 5 reviews. That's for an essay which takes about 3 hours to read - review for 80 extra minutes, and you can remember nearly all the details for about a month.

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michael_nielsen‏ @michael_nielsen Jun 26

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We think that with just a little extra marginal effort you'll remember those details - the entire body of knowledge - for more like a year. That's the benefit of exponential returns. But the prototype hasn't been out long enough to test that.

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michael_nielsen‏ @michael_nielsen Jun 26

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Here's the actual cumulative review time, rising roughly linearly (as we'd expect) with the number of repetitions.pic.twitter.com/GcbN9tjGoU

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michael_nielsen‏ @michael_nielsen Jun 26

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Interestingly, as questions are repeated, people seem to get a little faster at answering them. Here's the marginal review time, showing a slight decrease.pic.twitter.com/2ieATLswPV

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michael_nielsen‏ @michael_nielsen Jun 26

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That is, the marginal review time is going down, even though the time between reviews is increasing exponentially.

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michael_nielsen‏ @michael_nielsen Jun 26

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Similarly, the accuracy is getting better with repetition, even with the time between reviews increasing exponentially. At least in this sense, people are becoming more fluent.pic.twitter.com/UeGQPdT1Di

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michael_nielsen‏ @michael_nielsen Jun 26

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All very preliminary, of course, and there are many significant issues (esp. selection effects!) which we're working to address in other ways. Still, it's encouraging!

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michael_nielsen‏ @michael_nielsen Jun 26

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One curious thing about this demonstrated retention vs review repetitions plot: at 5 reviews, almost everyone who sticks with it has 2.5k days of demonstrated retention. For a worst-case outcome, that seems v encouraging!pic.twitter.com/WBaeqe4bJ3

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michael_nielsen‏ @michael_nielsen Jun 26

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Of course, "everyone who sticks with it" is a significant caveat. Maybe people who aren't going so well give up? We're investigating whether that might be the case or not.

2:36 PM - 26 Jun 2019