Spaced repetition is the least glamorous idea in language learning and the one with the most evidence behind it. The mechanism is simple enough to explain in a paragraph, which is worth doing, because understanding why it works changes how you use it.
The forgetting curve
Learn a new word today and you will not lose it all at once. You lose it fast at first — most of the loss happens within a day or two — and then more slowly. Hermann Ebbinghaus described this shape in the 1880s by memorising nonsense syllables on himself, and its rough form has held up ever since.
The important part is the second half: every time you successfully recall something just before you would have forgotten it, the curve gets flatter. The word decays more slowly than it did the time before. Recall it a few times at the right moments and the interval stretches from a day to a week to a month.
Why the timing is the whole trick
Review too soon and you learn almost nothing — the word is still fresh, so recalling it costs no effort, and the effort is what does the work. Review too late and you have genuinely forgotten it, and you are paying to learn it again from scratch.
A spaced repetition system exists to keep you in the narrow band between those two mistakes, for every word you are learning, without you having to track any of it. Get a word right, the next showing is pushed further out. Get it wrong, it comes back soon.
Where it goes wrong in practice
The scheduling is not what defeats people. What defeats them is that classic flashcard systems put the whole burden into one daily session, and the session grows: skip three days and you return to a backlog that is three times the size and no more appealing for the wait. The method is sound and the ritual is fragile.
Watch Your Language keeps the scheduling and throws away the session. The words appear in a widget on your Lock Screen and Apple Watch face, a few at a time, and the ones you have seen least recently come round most often. There is no queue to clear, so there is no backlog to come back to.
Using it well
- Learn words you have met, not words from a list. A word you first saw in a film or a conversation already has a hook; a word from a frequency list has none.
- Keep the units small. A single word or a short phrase schedules cleanly. A whole sentence you half-remember does not.
- Do not treat forgetting as failure. Forgetting is the signal the system runs on. A word you keep losing is a word the schedule is about to fix.
