The Forgetting Curve

In 1885, Hermann Ebbinghaus discovered something important: we forget almost everything we learn.

He tested himself by memorizing nonsense syllables and measuring how much he remembered over time. The curve was steep. Within 24 hours, he'd forgotten about 70% of what he learned. Within a week, almost everything was gone.

This isn't a flaw. It's a feature. Our brains evolved to filter information, not store everything. If you remembered every conversation, every face, every moment, you'd drown in noise.

But the forgetting curve shows something else: forgetting isn't linear. The rate of decay slows down over time. What you remember after a month will stay with you much longer than what you remember after a day.

This means the best time to review something isn't right after you learn it. It's right before you forget it. If you wait too long, it's gone. If you review too soon, you're wasting effort.

That's why spaced repetition works. It fights the forgetting curve at the optimal moment—when the memory is fading but still retrievable.

Most learning tools ignore this. They present information once and assume it sticks. But if we're serious about retention, we need systems that work with the curve, not against it.