The Forgetting Curve
How fast you lose what you just learned
Within one hour of learning something new, you've already lost more than half of it. Within 24 hours, roughly 70% is gone. This steep initial drop, the forgetting curve, was first described by Hermann Ebbinghaus in the 1880s and has been replicated countless times since. Memory decay isn't a flaw. It's a feature.
The good news is that the curve flattens dramatically after the first reviews. Each time you successfully retrieve a memory, you slow its decay, which is why spaced repetition is so much more effective than cramming. Apps like Anki use this to schedule reviews right before the predicted forgetting threshold, keeping memories alive with minimal effort. The same principle is why you remember childhood phone numbers you used a thousand times but can't recall a number you saw once last week.
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The Forgetting Curve