Think about it:
Remember your fourth grade class, when everybody had to pick an animal to study, checking out encyclopedia articles, cutting out pictures, maybe building a model of a habitat? Or what about sixth grade, when everyone in your class did a report on one of the US states? Or the high school literature class where each student presented about a different author?
You can name the animal, the state, the author, and probably tell me quite a bit about them, can't you?
I bet you remember what you taught (however awkwardly) better than you remember things that were taught to you by a professional.
The stress and adrenaline of standing up in front of your peers and presenting what you’d learned may have helped seal in the experience; strong emotion has a way of doing that.
This suggests to me that if we all need to learn more, maybe we all need to teach more.
After 30 days, students remember:
10% of what they hear
15% of what they see
20% of what they hear and see
40% of what they discuss
80% of what they do
90% of what they teach to others
From a study by the University of Indiana, quoted in the Thom and Joanie Shultz book The Dirt on Learning, p. 155.