Your Gut is Evidence

Douglas Crockford says:

So I think programming would not be possible without System I; without the gut. Now I have absolutely no evidence to support that statement, but my gut tells me it’s true, so I believe it.

Absolutely no evidence? I think that he has strong evidence to support that statement. I think that the gut feeling itself is evidence.


I have a question for you — in worlds where Douglas Crockford has a gut feeling about something related to programming, how often is that gut feeling correct? Probably a lot more than 50% of the time right? If so, then the gut feeling itself absolutely serves as evidence. Bayesian evidence at least.

What is bayesian evidence? To answer that, let’s get more abstract. Imagine that you observe X. Is X evidence for Y? Against Y?

  • “Well, in the past, when I observe X, Y seems to happen more than it otherwise would.” If so, then X is evidence for Y.
  • “In the past, when I observe X, Y seems to happen less than it otherwise would.” If so, then X is evidence against Y.
  • “In the past, when I observe X, I don’t see that Y happens any more or less often than it normally would.” If so, then X isn’t evidence for or against Y.

In this case:

X = Douglas Crockford has a gut feeling about something programming related.
Y = That gut feeling is true.

Given how accomplished he is, I’d guess that when he has gut feelings about programming, they’re true more than you’d otherwise expect them to be.


I didn’t always think this way. I used to have a very hard time accepting those sorts of gut level feeling as actual evidence. If I didn’t understand it on a deeper level, I wouldn’t be able to accept it as evidence.

Then, I read How We Decide, and it changed my mind. (And then I went and studied neuroscience in college and it really changed my mind.) There’s actual reason behind the gut feelings. They’re not random. It’s almost as if there’s this really smart little person in your head who interprets things and produces intuitions for you. You can’t watch this little person do his work, but that doesn’t mean that he isn’t there, and it doesn’t mean that he isn’t smart.

Never mind the analogy. That little person corresponds to actual neural pathways. I don’t know how to explain this concisely and without getting into the wiring, but the fact is that your brain is actually processing the information and producing intuitions accordingly. And it uses all the accumulated knowledge and reasoning ability it has to do its job. So to say “it’s just a gut feeling, it isn’t actually evidence” is absolutely wrong.

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