The Case for Mental Models

Sherlock Holmes asked Watson in A Study in Scarlet: “What the deuce is [the solar system] to me? You say that we go round the sun. If we went round the moon it would not make a pennyworth of difference to me or to my work.” Continuing in that vein, Holmes even announces his intent to unlearn this bit of information, “I shall do my best to forget it”.

Are Holmes’ remarks the reason why even very knowledgeable teachers struggle to teach their students? Because the student is thinking, “So? What do I do with that new bit of information you hurled at me?” After all, most people think of teaching the way Nobel-Prize winning physicist and professor Carl Wieman started:

“When I first taught physics as a young assistant professor, I used the approach that is all too common when someone is called upon to teach something. First I thought very hard about the topic and got it clear in my own mind. Then I explained it to my students so that they would understand it with the same clarity I had.”

But of course, that approach never works, does it? And why doesn’t it work? Because teachers assume that “expert-like ways of thinking about the subject come along for free or are already present”. So, it would seem necessary to also teach students how to process that information.

Charlie Munger brings out the same point when he talked about the importance of mental models:

“If the facts don’t hang together on a latticework of theory, you don’t have them in a usable form.”

Conversely, isolated facts don’t have much retention power.

Holmes even went to the extreme of advocating only taking in information that “fits” when he tells Watson:

“A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things, so that he has a difficulty in laying his hands upon it. Now the skillful workman is very careful indeed as to what he takes into his brain-attic.”

Of course, that’s a dangerous extreme. Munger knew that which is why he suggested:

“you’ve got to have multiple models”.

Otherwise, with just a single model, you risk becoming like the man whose only tool is a hammer. To him, every problem looks like a nail!

Epilogue: Of course, Holmes never truly practiced what he preached. He did know about astronomy, like the time he applied it in The Musgrave Ritual. Perhaps he was just playing devil’s advocate?