How does the Readwise spaced repetition algorithm work (Mastery)?
Admittedly, the Readwise spaced repetition algorithm (Mastery) is a bit of a black box compared to powerful spaced repetition software (SRS) such as Anki or SuperMemo. The reason for this is that we're trying to create a spaced repetition alternative that is extremely user friendly compared to the existing offerings, which have notoriously steep learning curves.
- We use a decaying algorithm based on a recall probability half-life rather than a date-based algorithm as found in Anki.
- The initial half-life of a Mastery `later` is 14 days. `Soon` is 7 days. `Eventually` 28 days.
- Once a highlight recall probability decays to 50% or lower, it becomes a candidate to be resurfaced in the latter half of your Daily Review.
If you have a lot of Mastery flashcards that are candidates to be resurfaced (probability of recall less than 50%), then those with the lowest recall probability will be resurfaced in your Daily Review.
You can see all your Mastery flashcards, their half-lives, and recall probabilities here: readwise.io/mastery.