Well, in my experience, it's true, and powerful.
The trick, of course, is what teaching something forces you to do before you get up at the lectern, in preparation. (That's assuming of course that you take the teaching assignment seriously enough to prepare.)
Let's look a little deeper, starting with why this works.
1. Teaching forces a focus on relationships and patterns, not just stand-alone facts.
To teach something well, you'll need to go beyond simply relating the "atomic level" facts or ideas involved; you'll need to explain out how those building blocks form patterns, sequences and relationships.
True understanding of something is achieved when individual instances can be abstracted to general truths. By first parsing your subject into major blocks of knowledge, then arranging them into logical sequence and pointing out key patterns and relationships (cause and effect…), you'll not only be preparing to present the material in a manner best able to be absorbed by your students, you'll be teasing out new insights that will deepen your understanding.
Finally, this organization of ideas into a logical framework renders it much easier to remember. (It's how our mind works.)
2. Teaching challenges you to identify and use Analogies and metaphors.
People learn best when they can relate new ideas to things they already know and understand. So, you'll want to use them in teaching your subject. Which means you'll have to find or invent them. Which in turn forces you to think about those patterns mentioned above yet again, from a fresh perspective. All of which will result in a further deepening of your understanding. If you can't come up with compelling analogies to get across your ideas, chances are you'll need to dig into the topic a bit deeper to find those underlying patterns and relationships.
3. Preparing to teach identifies gaps in your knowledge.
If you go about your preparations with care, you'll likely find that your knowledge of the subject is complete in some areas, less so in others. In effect, you'll be forced to take inventory of your own understanding. Gaps will stand out, and can be filled with study or further thought.
4. Teaching engages more of your mind.
While I'm not a cognitive scientist, I've done enough reading on the subject to claim with confidence that the sort of active information processing the brain does when organizing information per the above, and again when actually presenting it verbally, graphically or both, engages parts of our mind not engaged in more passive activities such as reading.
5. Teaching creates positive and negative incentives toward learning.
Nobody likes to be embarrassed, a state all-too-easy to find yourself in if you get up in front of a class to teach something and aren't prepared, or can't answer questions in a satisfying manner. When we're agree to teach something, we instinctively get this, and so are motivated to put in the effort required to do a great job.
A Tip: regardless of the sophistication of your audience, when you're finished preparing your lecture, ask yourself if the main ideas are presented so that an audience of bright thirteen year olds could understand them, and be engaged by them. If not, you still have more work to do in distilling down the concepts and finding compelling ways to present them.
One of my favorite fellow bloggers, David A. Brock (@davidabrock), recently called attention to the physics lectures given by Richard Feynman, as exemplary of how very complex (and potentially dry) ideas can be presented so as to achieve both understanding and emotional engagement. I first read and listened to them a couple of dozen years ago. David's spot on, and this standard of excellence is one to aspire to reach.
By the way, these same learning benefits accrue whether you teach a course, write a serious paper, article or blog post (I'm learning something this way every time I do one of these) or step up to do some intensive one-on-one coaching for a promising team member.
Regardless of which vehicle you choose, in addition to deepening your understanding, you'll realize a powerful set of side benefits. You'll:
- Improve your communications skills
- Enhance your standing in your peer group, industry or community
- Gain the satisfaction of helping others
- Have fun!
So, next time you want to learn something, find a way to teach it. It'll be good for you.