The science
Why spaced repetition works, and what Orbilu adds
A century of memory research, the open-source model that puts it to use, and the parts Orbilu does for you. In plain words.
Your brain is designed to forget
That is a feature. Most of what you meet in a day, a face on a train, a one-time code, an overheard name, stops mattering the moment it has gone, so your brain quietly lets it fade.
In 1885 Hermann Ebbinghaus measured that fading and drew the first forgetting curve: steep at first, then flattening. Without another encounter, most new material is gone within a week. A new word in a language you are learning gets the same treatment, unless something tells your brain it matters.
That something is meeting it again, at the right moment.
Try it: time three reviews
Each review resets the curve and makes it flatter, so the word sits more steadily in memory. Tap the chart to place up to three reviews and watch what happens over 30 days. The curve is a simple model of forgetting, not FSRS: the shape is real, the numbers are illustrative.
No reviews. Most of the word is gone within a week.
Spaced repetition: the right moment, not more time
Meet a word again just before you would forget it and your brain takes the hint: this one matters. Each well-timed review makes the memory last longer, so the next review can wait longer still. Days become weeks become months.
This is one of the best-replicated findings in psychology. A 2006 review of more than 300 experiments found spaced practice beat massed practice almost every time, for every kind of material tested.
Crammed: 4% on day 30 · Spaced: 98% on day 30
None of it needs an app. Paper cards in a shoebox work. What is hard is the timing: knowing, for hundreds of words at once, which ones are about to slip today. That is bookkeeping no one wants to do by hand.
Active recall: asking beats re-reading
Re-reading a word feels like learning, but pulling it out of memory is what strengthens it. In a classic 2006 study, students who were tested on a passage remembered far more a week later than students who re-read it, even though the re-readers felt more confident.
That is why every card asks before it tells. You see the word, or hear it, and reach for the meaning. Then you grade yourself: Again, Hard, Good or Easy.
Do you know this word?
How Orbilu models your memory
Orbilu schedules with FSRS, the Free Spaced Repetition Scheduler: open source, built into modern Anki, and trained on hundreds of millions of real reviews. For every word it keeps three numbers.
Every review updates the three, and the next review is set for the day retrievability is about to drop below 90 percent. Words you know drift further apart; shaky ones return sooner. Miss a day and nothing breaks: the numbers simply pick up where they were, and the reviews are retimed around when you show up.
What Orbilu adds on top of the model
FSRS answers one question: when. Orbilu answers the rest.
Words chosen for your reasons
Tell Orbilu your level and what the language is for. Each day she picks a few new words, about half of them for your goal and the rest the words everyone needs.
Two cards, written for you
Every word gets a translation, a pronunciation guide, a sentence at your level and audio, and becomes two cards: one to recognise it, one to produce it.
The signals behind your grade
You still choose Again, Hard, Good or Easy. Orbilu also notices how long you took, whether you replayed the audio and what you typed, and suggests Hard when you hesitated.
A note, and a steadier pace
After each session Orbilu writes you a short note about what she saw and adjusts the pace: more new words when you are ready, fewer when you are not.
No decks to build. I keep the schedule. You just show up.
Orbilu and Anki
Anki proved the method. It is where many of us, Orbilu’s founder included, first met spaced repetition, and it still runs the same FSRS model Orbilu uses. The difference is everything around the model.
What Anki asks of you, and what Orbilu does instead
- Anki asks you to Find your own words and type them in
- Orbilu Picks each day’s words for your level and your goal
- Anki asks you to Write the back of every card
- Orbilu Has a language model write the translation, a pronunciation guide and a sentence at your level
- Anki asks you to Hunt for audio
- Orbilu Says every word aloud
- Anki asks you to Grade every card yourself, with nothing else to go on
- Orbilu Still asks for your grade, and reads how long you took and when you hesitated to suggest Hard
- Anki asks you to Decide what to add next
- Orbilu Adjusts the pace and the mix after every session
Orbilu is for the words. The language itself still comes from a tutor, a book, a series you watch, a conversation. Those give you new words; Orbilu makes sure they stay.
The research
- Ebbinghaus, H. (1885). Über das Gedächtnis. The original forgetting-curve experiments. Read it
- Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks: a review and quantitative synthesis. Psychological Bulletin, 132(3), 354–380. DOI
- Roediger, H. L., & Karpicke, J. D. (2006). Test-enhanced learning: taking memory tests improves long-term retention. Psychological Science, 17(3), 249–255. DOI
- FSRS, the open-source Free Spaced Repetition Scheduler. Project
Start with the words you will meet tonight.
I’ll plant your first words tonight.
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