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Why spaced repetition?
Slonto schedules review of your lessons at J+1, J+7, J+30 so you remember for good. Here is the science behind it — in plain language.
The problem in one sentence
Without repetition, about 70% of learned content is forgotten within two weeks. And more than half of online learners drop out before even that. The real problem with online courses is not acquisition marketing: it's retention — learner retention (they don't finish) and knowledge retention (they forget).
Dropout: ~60% of learners quit within 2 weeks
Dropout rates are massive in unguided online courses:
- About 50% of all dropouts happen within the first two weeks. The dropout curve is exponential at the start.
- MOOC completion rates are often only 2 to 15%, and the risk of quitting is highest in the first week.
- ISTF barometers (France/Europe) report over 60% dropout in untutored programs, 60% of which have completion rates below 10%.
- Main factors cited by learners: lack of time, lack of motivation, isolation, course design.
"60% within 2 weeks" is a realistic — even conservative — estimate. Early dropout is the norm, not the exception.
Forgetting: ~70% of content forgotten within 2 weeks without review
This is the forgetting curve, discovered by Hermann Ebbinghaus in 1885 and confirmed by modern scientific replications (Murre & Dros, 2015).
| Delay without review | Forgotten | Retained |
|---|---|---|
| 1 day | ~67% | ~33% |
| 2 days | ~72% | ~28% |
| 1 week | ~75% | ~25% |
| 2 weeks | ~75–79% | ~25% or less |
| 31 days | ~79% | ~21% |
Exact percentages vary by content type, but the dynamic stays the same: without review, most of it disappears within days or weeks.
Why spaced repetition is the answer
- Review at the right moment: each review strengthens memory and pushes the forgetting curve back.
- Space increasingly: the better you know a card, the less often it needs to come back.
- Short and regular: a few minutes a day beats a massive but rare re-read.
The literature (cognitive psychology + e-learning) converges: active, spaced review is the #1 lever for knowledge retention.
How Slonto applies it
Slonto's SRS model is deliberately simple and readable, and builds directly on this science:
The card comes back the next day, right when forgetting begins (~67% lost at 24h without a reminder).
Second reminder, when the curve drops to ~75% forgotten.
Third milestone for durable anchoring.
Beyond that, the interval keeps growing (ease factor, like in Anki) up to a maximum of one review per year.
Two buttons are enough
- I knew it "I knew it": the card moves to the next milestone, spacing gets longer.
- I didn't know "I didn't know": the card comes back the next day — consolidate before spacing again.
What it changes for you
| Without spaced repetition | With Slonto |
|---|---|
| I buy, I start… then I forget. | I come back every day for a short session. |
| I cram before the exam, then forget. | I review in small spaced doses, right on time. |
| I lose motivation within the first two weeks. | The daily reminder and the streak keep me going. |
| I retain ~25% after two weeks. | Each review pushes the curve back: long-term retention rises clearly. |
Sources
The data above summarize robust, measured trends, including:
- Scientific replication of the forgetting curve — Murre & Dros (2015), PLOS ONE (journals.plos.org)
- Studies on MOOC dropout — Journal of Computing in Higher Education (link.springer.com)
- ISTF barometers on professional digital learning (France/Europe data)
- Completion-rate analyses across millions of e-learning enrollments
A note of caution
Exact numbers vary across studies, formats and content. Slonto relies on these data as solid trends, not absolute promises. That's why the model is measurable and evolvable: the J+1/J+7/J+30 matrix is deliberately simple, and the algorithm can evolve (e.g. FSRS-5, the one Anki uses) without changing your experience.