The Forgetting Curve and How Memory Works

In 1885, a German psychologist named Hermann Ebbinghaus conducted one of the most important experiments in the history of learning science. He memorised lists of nonsense syllables — meaningless combinations like "DAX," "BOK," and "ZUP" — and then tested himself at various intervals to see how much he could remember.

What he discovered was startling: memory decays at an exponential rate. Within the first hour, he had already forgotten more than half of what he had learned. Within a day, roughly two-thirds was gone. Within a month, nearly 80% had vanished.

This pattern of rapid initial forgetting followed by a gradual levelling off became known as the forgetting curve, and it remains one of the most replicated findings in all of psychology.

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The Forgetting Curve in Detail

The forgetting curve is not a straight decline. It follows an exponential pattern:

• After 20 minutes: roughly 40% forgotten
• After 1 hour: roughly 55% forgotten
• After 1 day: roughly 65–70% forgotten
• After 1 week: roughly 75% forgotten
• After 1 month: roughly 80% forgotten