The Mental Model Fallacy

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If you're here from HN, and you find this criticism bizarre, you should probably read this short summary post first.

This is a companion discussion topic for the original entry at https://commoncog.com/the-mental-model-fallacy/
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“When Buffet studies a company, he doesn’t see a checklist of mental models”. Charlie Munger is literally quoted as saying he does (in PCA, “No wise pilot, no matter how great his talent and experience, fails to use a checklist.”)

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That’s what Charlie says he does. What he actually does is vastly more interesting and idiosyncratic, and it is worth chasing down actual examples of him thinking through problems, not reading speeches describing how he solves problems.

Janet Lowe’s biography of Charlie is a good place to start. Peter Kaufman’s recollections of Charlie is also not bad. There’s a wonderful sequence in A Conversation with Charlie Munger & John Collison - Colossus where he reasons about the dorm design problem that is just fascinating and so damn sharp.

That said, if you have good results applying mental models in a mechanical way, I’m all ears — I just can’t seem to get it to work for me.

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Thanks, I’ll check those books out in due course (agree the interview is v good). How certain are you of this point though? He’s pretty explicit about it, and on several occasions (so much so that checklists are somewhat synonymous with munger in investing circles).

“How can smart people so often be wrong? They don’t do what I’m telling you to do: use a checklist to be sure you get all the main models and use them together in a multimodular way"

“You need a different checklist and different mental models for different companies. I can never make it easy by saying, ‘Here are three things.’ You have to derive it yourself to ingrain it in your head for the rest of your life.”

“Use of the scientific method and effective checklists minimizes errors and omissions.”

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Fairly certain! It’s been seven (eight?) years now that I’ve tried to put Munger’s various recommendations to practice. I’ve mostly failed. The only bit about Munger’s cognition that I’ve gotten to work for me is the CFT stuff — How Note Taking Can Help You Become an Expert - Commoncog — and that required an external theory of expertise to give me a mechanism for Munger’s ability to reason by analogy.

I mean — you’ve listened to that interview on ILTB. What checklist or series of mental models did Munger use for that dorm solution? It seems to me he reasoned by analogy more than he did anything like a model search — he looked for domains that had to solve similar problems (ship design). There was some cue in the problem that he noticed, then he found an analogous design problem in an unrelated domain, and then he broke it down by asking “why does it work on ships, and can that apply to buildings?”

You can actually find comments from Munger’s various friends over the decades — they all say that Munger’s mind is quite singular. So perhaps it might be a matter of mental wiring. The exhortation to use checklists and mental models might work for his brain wiring (again, I am sceptical — I don’t think is the full picture; I think this is what he thinks he does), but the true test is if it can work for you? If it can, I would like details. I just can’t get it to work for me.

There’s something here that falls out of the broader expertise research field that I’ve covered in Commoncog. Experts are not good at metacognition. There is a reason why the researchers in Accelerated Expertise use Cognitive Task Analysis — a form of tacit knowledge elicitation. The other bit that falls out of that body of work is that experts don’t actually do anything as simple as checklists (there was a whole movement in the 90s to extract knowledge and turn it into checklists; this failed miserably because expertise is more than static checklisting — it is about adaptation[1]). In fact experts often think that they’re using a checklist, but in reality they’re doing recognition-primed decision making, which is richer, faster, and more adaptable.

Ultimately, this doesn’t matter as much: I think there is limited value to debate what Munger has said (the historical record is very clear that he believes in checklists and mental models; also that he is very believable). The true test is if this is useful — can you get Munger’s recommendation to work for you? And on that note, I’m still stuck.

Edited to add [1] is actually one of the most important papers in Naturalistic Decision Making.

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