Spaced Repetition: The Science Behind Our Vocabulary System

You learn a word on Monday. You remember it on Tuesday. By the following Monday, it's gone. This isn't a memory failure — it's how human memory is designed to work.

The forgetting curve

Hermann Ebbinghaus showed in 1885 that we forget most of what we learn within 24 hours unless we review it. The forgetting curve is exponential: without review, you retain 58% after 20 minutes, 44% after an hour, and 21% after a day.

How spaced repetition fights the curve

Each time you successfully recall a word, the forgetting curve resets — but at a shallower slope. Review at the right moment (just before you'd forget it) and the next forgetting curve extends from days to weeks to months. The SareLearn algorithm calculates this interval individually for each word based on your response time and accuracy.

What 'active recall' means for language learning

Passive review (reading a word and its translation) doesn't reset the forgetting curve effectively. Active recall — being shown the word and trying to retrieve its meaning before seeing the answer — does. This is why SareLearn shows you the target word first, requires you to answer, then reveals the translation.

15 minutes a day beats 2 hours on weekends

Spaced repetition is time-sensitive. Reviewing 100 words at the right intervals for 15 minutes daily is 3× more effective than 2-hour weekend sessions. Consistency matters more than intensity. The algorithm ensures each session shows you the words that are most at risk of being forgotten today.