Forgetting curve
The forgetting curve, described by Hermann Ebbinghaus, is the pattern in which memory of new material drops sharply over the hours and days after you learn it, unless you review it. Each well-timed review flattens the curve so the same facts decay more slowly.
Ebbinghaus found that people forget most of what they learn within a day or two. Without review, you can lose 70 to 80 percent of new material after 24 hours. The curve matters because it explains why cramming the night before fails: the memory was never given a chance to settle, so it drains out fast.
The fix is not more rereading. It is spacing your reviews and making them active. Each time you pull a fact back from memory just before you would forget it, the curve gets flatter and the next safe gap gets longer. A common misconception is that the curve is fixed. It is not. The shape changes every time you review.
You learn the Krebs cycle in a Tuesday lecture. If you never look at it again, by Thursday most of the steps are gone. Instead you quiz yourself that evening, again on Friday, then the next week. Each round feels easier, and by the exam the cycle stays put.
- 1Review new material the same day you first learn it, while it is still fresh.
- 2Space the next reviews at growing gaps: one day, then a few days, then a week.
- 3Make every review active. Quiz yourself or write from memory instead of rereading.
- 4Review a topic right before you expect to forget it, not long after.
- 5Track which topics feel shaky and give those shorter gaps.
Put it to work on your own course
From your uploaded lectures and PDFs, Bo builds flashcards, quizzes and practice exams, and every answer you give updates per-concept mastery with time decay. That decay mirrors the forgetting curve, so Bo can surface the concepts you are about to forget and build targeted practice around them.
Get started freeGet started freeHow quickly do you forget what you study?
Ebbinghaus found people lose about half of new material within an hour and 70 to 80 percent within a day if they never review it. The exact speed depends on how meaningful the material is and how well you understood it. Spacing reviews slows this loss dramatically.
Is spaced repetition better than rereading?
Yes. Rereading feels productive but barely dents the forgetting curve, because you are recognizing the text, not recalling it. Spaced repetition forces active recall at growing intervals, which is what actually flattens the curve and moves facts into long-term memory.