A Flaw in the Model

My mother, a career educator, has become one of those elderly Facebook ladies who posts what they take to be well-meaning things that would make me want to pull out my hair if I had any. I do not argue with her posts, which would seem churlish and lacking in filial piety, and you never win by arguing on social media in any case. The other day, for example, she posted a meme to the effect of, "If I hear that a woman was arrested for stealing diapers, I don't want to see her prosecuted. I want to know if she also need formula." It sounds nice, and I can understand the generous spirit intended, but... well, I don't have to explain to any of you what problems lie there.  

This one was posted without any accompanying evidence that the cited percentages were true or backed up by anything at all. That is one problem.

Another problem is this: let's say arguendo that this is an accurate picture. This is about retention, not the correctness of your instruction. So if you learn by teaching, you will retain 90% of the information you teach. How did you know that information before you taught it? Well, you didn't; you learned it by teaching it. Thus, you are retaining 90% of God knows what you are teaching the class (who, if you are teaching by lecture, will thankfully only retain 5% of whatever it is you're spewing at them). 

It's definitely true that figuring out how to explain something often builds bridges in the mind that deepens one's own understanding of that thing. However, there has to be an understanding of that thing to deepen. That has to be acquired before you start trying to teach the subject downrange. 

This might be a pretty good model if you reversed it, and treated it as stages in one's own learning rather than a question about how to retain what you've learned. Start by attending lectures, do quite a lot of reading, I don't know if I agree that audio-visual actually improves over reading; personally I think reading works better, but that may vary somewhat by individual. Anyway, carry on through the stages and at some point you will know enough to try to teach it. When that happens, yes, you will deepen your understanding further yet. However, you have to build the understanding before you either you or your students will benefit from you teaching anything.