What is spaced repetition? How the Leitner system helps you remember

You memorize 50 new words on Sunday night, and by Wednesday most of them are gone. Your memory isn't bad — that's simply how the brain works. The good news is that a simple method helps you remember for longer without studying more: spaced repetition.

The forgetting curve

In the late 19th century, psychologist Hermann Ebbinghaus tested himself on hundreds of nonsense syllables and tracked how quickly he forgot them. The result was the forgetting curve: most new information fades very quickly in the first hours and days, and then the rate of forgetting slows down.

His more important finding: every time you review right before you would forget, the curve gets flatter. The next review can come later, and you still remember.

What is spaced repetition?

Spaced repetition means reviewing at growing intervals:

• Something you just learned is reviewed after one day.
• If you still remember it, the next review comes later — a few days, a week, then a few weeks.
• If you forget it, the interval goes back to short to rebuild the memory.

Compared with cramming in one long session, this takes less time and keeps knowledge longer, because your effort goes only to what is at risk of being forgotten.

The Leitner system: spaced repetition with boxes

In 1972, journalist Sebastian Leitner proposed a very visual way to apply it: sort your flashcards into several boxes.

1. Every new card starts in box 1.
2. Answer correctly and the card moves up to the next box.
3. Answer wrong and the card goes back to box 1, wherever it was.
4. The higher the box, the longer until the next review.

Cards you know well gradually "climb" and rarely appear, while hard cards keep coming back until you truly know them.

How Doopi uses the Leitner system

Doopi uses six boxes with review intervals of 1, 2, 4, 7, 14 and 30 days. While reviewing:

• Swipe right (or press →) when you know it — the card moves up a box.
• Swipe left (or press ←) when you don't — the card returns to the first box and comes back tomorrow.
• Slipped? Press Undo (the Z key) to grade again.

You never have to track which cards are due: every day Doopi gathers exactly the ones you need to review.

Tips for better reviews

• Review a little every day. Fifteen steady minutes beat two hours crammed into the weekend.
• Grade honestly. Only mark a card as known when you recall it without guessing.
• One idea per card. Short, clear cards are easier to remember than long paragraphs.
• Add context. An example sentence or an image helps a new word stick.
• Connect words. Learning word families, synonyms and antonyms builds a network instead of isolated facts.

Spaced repetition isn't magic, but it makes every minute of study count. Try a small deck and review it daily for a week — you'll notice the difference.