Learning Science26 June 20254 min read

The Forgetting Curve: Why You Lose 70% of New Information Within 24 Hours

In 1885, Hermann Ebbinghaus memorised lists of nonsense syllables and then tested his own recall at regular intervals. The results formed what is now called the forgetting curve — and they should make you rethink how you study.

What the Curve Shows

Ebbinghaus's own data showed retention dropping to around 44% after just one hour — already more than half gone. By 24 hours it was down to roughly a third. By six days later, without any review, retention had settled around 25% of what he'd originally learned.

This isn't a personal failing. It's the default setting of human memory. Information that isn't used, revisited, or connected to existing knowledge gets deprioritised. Your brain treats it as noise, and noise gets cleared.

Why Passive Review Doesn't Help Much

Re-reading notes feels productive because it's familiar. You recognise the content; the words look right. But recognition and recall are different cognitive processes. Recognition is easy — of course you remember it when you're looking at it. Recall is what happens when the book is closed and you need the information.

Passive review — rereading, highlighting, listening again — produces recognition, not recall. It feels like studying, but it doesn't produce the neurological changes that make information durable.

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