Spaced Repetition
Beat the forgetting curve by testing at widening intervals
- Difficulty
- Easy
- Time to result
- ~months to results
- Steps
- 4
- Confidence
- 93%
Spaced repetition combats the forgetting curve first plotted by Ebbinghaus in the 1800s, who memorised nonsense words and charted how fast he lost them: a steep initial drop that slows over time. The mechanism is to re-test yourself just as a memory is starting to fade, correct any errors, which resets retention toward 100%, and crucially each repetition makes the curve decay more slowly. So you review at expanding intervals: a day or few days after first learning, then a week, then a month, then six months. Facts you 'accidentally' encountered many times (like Paris being the capital of France) are already spaced into permanence; deliberate spacing does the same for anything. Tools like Anki automate the scheduling.
Origin
The forgetting curve comes from Hermann Ebbinghaus (1880s). Ali Abdaal frames the modern study application, drawing on Make It Stick, from his medical-school revision.
Core principles
- 01Forgetting follows an exponential decay curve (Ebbinghaus)
- 02Each successful recall resets memory toward 100% and flattens the curve
- 03There is no photographic memory; strong memorisers simply repeat
- 04Expecting one-time recall is absurd in any other skill domain
- 05Repeated exposure over long periods moves facts into long-term memory
How to run it
- 1
Learn and test the same day
After first learning a topic, test yourself on it once to establish the initial memory.
- 2
First short-interval review
Return to the topic a day or a few days later and try to recall it before checking.
Pro tip Getting it wrong is fine; the correction after retrieval is what resets the curve.
- 3
Widen the intervals
Space subsequent reviews further apart: roughly a week, then a month, then six months, as recall gets more reliable.
Watch out Do not abandon a topic after one good recall; a single pass rarely reaches long-term memory.
- 4
Automate where possible
Use a spaced-repetition app such as Anki to schedule reviews for you and keep the daily queue moving.
Pro tip Consistency matters more than volume; a little every day beats cramming.
In the wild
Ali contrasts two facts. The capital of France being Paris is something you have encountered so many times across your life, through countless incidental means, that you will never forget it: spaced repetition has been applied to it by accident. By contrast, if someone told you the capital of a random country right now, you would forget it unless you met that fact again and again. Deliberately re-testing a topic at widening intervals reproduces the same effect on purpose, pushing knowledge into long-term memory until it becomes as durable as 'Paris'.
→ Facts move from fragile short-term memory into permanent long-term memory.
Common mistakes
Believing in photographic memory
Assuming classmates who 'remember instantly' have a gift; in reality they are quietly repeating and revising, and comparing yourself to a myth is demoralising.
Expecting one-time recall
Treating a single exposure as enough contradicts every other skill; you would never expect to nail a piano piece or tennis swing on the first try.
Is it for you?
Best for
Large volumes of factual material that must be retained over months, such as medical knowledge or vocabulary.
Not ideal for
Skills learned by application rather than recall, where doing varied problems matters more than timed review.
From the transcript
“the idea of space repetition is that it combats the forgetting curve”
“initially when we learn something we then want to repeat the testing of it fairly quickly maybe a day or a few days later and…”
From the episode
How To Learn & Remember Anything, Fast - Ali Abdaal - #231
Ali Abdaal