How does spaced repetition work?
Why seeing a card again just before you’d forget it makes it stick.
PointsGame
Most of us revise flashcards the same way: go through the deck, then go through it again. It feels like work, but a lot of that time goes on cards you already know.
Spaced repetition goes through the same cards differently. It brings each one back just before you’d forget it, so your time goes on the cards that need it. Here’s how it works, with things to try as you read.
Most flashcards go straight to the back
On Studyclix, for example, you flip each card and press Next until the deck is done, then start it again. So every card comes back at the same pace, whether you knew it or not, and nothing is scheduled for another day.
That’s fine the first time through a topic. But once you know most of a deck, going round again means most of your time goes on cards you already know, while the few you don’t wait their turn behind them. Press a few times, or , and watch where each card goes.
Figure 1 of 4
One deck, two ways
- Enzyme
- Osmosis
- Mitosis
- Catalyst
- Meiosis
- Nucleus
- Diffusion
- Ribosome
0 known cards repeated
- Enzyme
- Osmosis
- Mitosis
- Catalyst
- Meiosis
- Nucleus
- Diffusion
- Ribosome
0 known cards repeated
Seeing a card again straight away barely helps
You forget on a curve: quickly at first, then more slowly. Seeing a card again while you still remember it adds almost nothing. Seeing it just as you’re starting to forget is what makes it last.
Take four goes at one card. Put them and the memory lasts about two days. the way we schedule them, and it lasts about six weeks. You can drag the goes to try your own.
Figure 2 of 4
Same four goes, two ways
Each card gets its own schedule
Each time you answer, PointsGame works out when your chance of remembering that card will have dropped to 90%, and brings it back then. We use FSRS, the scheduler built into Anki, which was fitted to hundreds of millions of real reviews.
Only Wrong counts as forgetting. Hard, Right and Easy all count as remembering, with different effort, so each sends the card further away. Press a few times, then , and watch the gap grow and then shrink.
Figure 3 of 4
Try it
Day 0 · Biology
What is osmosis?
Say the answer in your head, then show it and pick how it went.
A few new cards a day go a long way
Because each card comes back less often every time, your reviews grow slowly while the number of cards you know keeps climbing. At , two months gets you 600 cards for about 50 a day. At , it’s 1,800 cards for about 150.
Miss a day and nothing breaks: the cards wait for you, there are just a few more of them. A little every day beats a lot once a week.
Figure 4 of 4
What a few new cards a day adds up to
- New cards, twice on their first day
- Reviews