What is the forgetting curve?
The forgetting curve describes how quickly we lose newly learned information over time. German psychologist Hermann Ebbinghaus introduced it in his 1885 book *Über das Gedächtnis* (*Memory*). The curve drops steeply in the first hours and then flattens out.
- Researcher
- Hermann Ebbinghaus
- Published
- 1885, Über das Gedächtnis
- Method
- Measured time saved relearning lists of nonsense syllables
- Key finding
- Forgetting is rapid at first, then slows
Ebbinghaus’s experiments
To avoid the influence of meaning, Ebbinghaus memorized lists of nonsense syllables such as "DAX" or "BOK." After a delay he relearned each list and measured how much time he saved compared with the first learning, a measure called savings. He tested delays of 20 minutes, 1 hour, 9 hours, 1 day, 2 days, 6 days and 31 days.
What the replication shows
Claims like "you forget 70% within a day" circulate widely, but they shouldn’t be taken literally. Murre and Dros (2015) replicated Ebbinghaus’s procedure and found a very similar curve, but the exact numbers depend heavily on the material, the learner and how memory is measured. Meaningful, well-understood material is retained far longer than nonsense syllables.
Interestingly, the replication found a small upturn around the one-day mark, which the authors suggested might reflect memory consolidation during sleep.
| Time since learning | Pattern |
|---|---|
| 20 minutes–1 hour | Fastest forgetting |
| Around 1 day | Decline slows; possible sleep effect |
| Days to a month | Slow continued decline; some material lasts |
Study strategies that slow forgetting
- Review briefly the same day. A quick recall during the steepest part of the curve pays off.
- Expand the gaps. Review after 1 day, 3 days, 1 week and 2 weeks. See the spacing effect.
- Recall instead of rereading. Closing the book and quizzing yourself, or retrieval practice, produces longer-lasting memory.
- Connect to meaning. Link new ideas to what you already know and create examples.
- Sleep. A good night’s sleep helps consolidate memory far better than an all-nighter.
Frequently asked questions
- What is the Ebbinghaus forgetting curve?
- A curve showing how memory for new information declines over time, quickly at first and then more slowly.
- Do we really forget 70% within a day?
- That figure loosely reflects memory for nonsense syllables in the original experiments; meaningful, understood material is remembered much longer.
- What review schedule beats the forgetting curve?
- Review the same day, then at expanding intervals such as 1 day, 3 days, 1 week and 2 weeks, actively recalling the material each time.
References
- Ebbinghaus, H. (1885). Über das Gedächtnis: Untersuchungen zur experimentellen Psychologie. Leipzig: Duncker & Humblot. (English trans. 1913, Memory: A Contribution to Experimental Psychology.)
- Murre, J. M. J., & Dros, J. (2015). Replication and analysis of Ebbinghaus’ forgetting curve. PLOS ONE, 10(7), e0120644.