Good question! 🙂
The algorithm works like this:
- When you successfully review a word, the system records how long you’ve remembered that word for.
- For example, let’s say you learn a word in the morning and then log in and review it 8 hours later. The system will record that you’ve successfully remembered the word for 8 hours.
- When more time has passed than twice the time that you’ve successfully remembered a word, the system has you review the word again.
- For example, if more than 16 hours have passed for the word that you learned in the first example, you’ll be prompted to review it again. (Because 8 * 2 = 16).
The beauty of this system is that it works well no matter what time you log in to review your vocabulary. Continuing with the above example, let’s say that you successfully reviewed a word 8 hours after you learned it, but then you don’t log in to review your vocabulary for 2 days. If you then successfully review the word, the system will record you as having successfully remembered it for 2 days and won’t have you review it again for another 4 days! Did you go on vacation for 2 weeks but still remember your vocabulary? Great, the system won’t prompt you again for 4 weeks! 🙂
To answer your question: Level up shows you words that the spaced repetition system thinks you should review. That is, it shows you words where more than succesfully_remembered_time * 2 time has passed. (If you successfully remembered a word for 3 days, then Level up would show you the word when 6 more days have passed)
