Learning isn't an event. It's a rhythm.

In 1885, Hermann Ebbinghaus measured on himself how quickly we forget. The result is uncomfortable: without repetition, what we learn is gone surprisingly fast.

When we plan a course, we tend to think about the moment of teaching, about good slides and a clear explanation. What happens to the material afterwards is often left to chance. But how much sticks only shows in that afterwards.

A self-experiment with nonsense syllables

Ebbinghaus was both experimenter and subject. He memorised lists of nonsense syllables and tested how much remained after intervals ranging from 20 minutes to 31 days. His measure was the savings method: how much less effort does it take to learn a list again?

The result is the forgetting curve. It drops steeply at first and then levels off. In 2015, Murre and Dros repeated the experiment, again with a single subject, over roughly 70 hours. Their results were similar to Ebbinghaus’ original data.

What the curve doesn’t tell you

Be careful with precise percentages that circulate online, such as how much you supposedly forget after a week. Ebbinghaus’ figures apply to nonsense syllables in a self-experiment and don’t transfer neatly to course content. That’s why the video shows the curve as a schematic, without measured values.

Meaningful material is retained better. Ebbinghaus himself found that stanzas from Byron’s “Don Juan” needed only a fraction of the repetitions. But the principle holds: without repetition, meaningful material fades too.

Every repetition pulls the curve back up

The good news comes from Ebbinghaus as well. When he relearned the same list on several days, his savings grew. Put simply: every repetition pulls the curve back up, and afterwards it falls more gently than before.

Current learning research points the same way. In 2013, Dunlosky and colleagues rated common learning techniques by how useful they are. Distributed practice and practice testing came out on top, while rereading was rated low. As Dunlosky puts it, almost any kind of practice test helps.

Three things for your courses

1. Plan repetition, spaced over days and weeks, instead of cramming everything into one day.
2. Test instead of rereading. Actively recalling something sticks better than going over the text again.
3. Build in short moments of recall, for example a quiz at the start of the next lesson.

A quiz to start with

Open your next lesson with three to five short questions: two on the previous lesson, one on a topic from a few weeks back. No grades, and the answers follow straight away. It takes a few minutes and combines the two techniques that scored best in Dunlosky’s review: testing and spacing.

For the course plan itself: take your current plan and mark, for every important topic, when it comes up a second time after it was first taught. Wherever there is no mark, the course is quietly planning for forgetting.

Learning is not a one-time event. It’s a rhythm.