Steve Byrnes’s Shortform

Steven Byrnes

This is a special post for quick takes by Steven Byrnes. Only they can create top-level comments. Comments here also appear on the Quick Takes page and All Posts page.

Dear diary...

[this is an experiment in just posting little progress reports as a self-motivation tool.]

1. I have a growing suspicion that I was wrong to lump the amygdala in with the midbrain. It may be learning by the same reward signal as the neocortex. Or maybe not. It's confusing. Things I'm digesting: https://twitter.com/steve47285/status/1314553896057081857?s=19 (and references therein) and https://www.researchgate.net/publication/11523425_Parallels_between_cerebellum-_and_amygdala-dependent_conditioning

2. Speaking of mistakes, I'm also regretting some comments I made a while ago suggesting that the brain doesn't do backpropagation. Maybe that's true in a narrow sense, but Randall O'Reilly has convinced me that the brain definitely does error-driven learning sometimes (I already knew that), and moreover it may well be able to propagate errors through at least one or two layers of a hierarchy, with enough accuracy to converge. No that doesn't mean that the brain is exactly the same as a PyTorch / Tensorflow Default-Settings Deep Neural Net.

3. My long work-in-progress post on autism continues to be stuck on the fact that there seem to be two theories of social impairment that are each plausible and totally different. In one theory, social interactions are complex and hard to follow / model for cognitive / predictive-model-building reasons. The evidence I like for that is the role of the cerebellum, which sounds awfully causally implicated in autism. Like, absence of a cerebellum can cause autism, if I'm remembering right. In the other theory, modeling social interactions in the neurotypical way (via empathy) is aversive. The evidence I like for that is people with autism self-reporting that eye contact is aversive, among other things. (This is part of "intense world theory".) Of those two stories, I'm roughly 100% sold on the latter story is right. But the former story doesn't seem obviously wrong, and I don't like having two explanations for the same thing (although it's not impossible, autism involves different symptoms in different people, and they could co-occur for biological reasons rather than computational reasons). I'm hoping that the stories actually come together somehow, and I'm just confused about what the cerebellum and amygdala do. So I'm reading and thinking about that.

4. New theory I'm playing with: the neocortex outputs predictions directly, in addition to motor commands. E.g. "my arm is going to be touched". Then the midbrain knows not to flinch when someone touches the arm. That could explain why the visual cortex talks to the superior colliculus, which I always thought was weird. Jeff Hawkins says those connections are the neocortex sending out eye movement motor commands, but isn't that controlled by the frontal eye fields? Oh, then Randall O'Reilly had this mysterious throwaway comment in a lecture that the frontal eye fields seem to be at the bottom of the visual hierarchy if you look at the connections. (He had a reference, I should read it.) I don't know what the heck is going on.

2Steven Byrnes6y

I was just writing about my perspective here; see also Simulation Theory (the opposite of "Theory Theory", believe it or not!). I mean, you could say that "making friends and being nice to them" is a form of manipulation, in some technical sense, blah blah evolutionary game theory blah blah, I guess. That seems like something Robin Hanson would say :-P I think it's a bit too cynical if you mean "manipulation" in the everyday sense involving bad intent. Also, if you want to send out vibes of "Don't mess with me or I will crush you!" to other people—and the ability to make credible threats is advantageous for game-theory reasons—that's all about being predictable and consistent! Again as I posted just now, I think the lion's share of "modeling", as I'm using the term, is something that happens unconsciously in a fraction of second, not effortful empathy or modeling. Hmmm... If I'm trying to impress someone, I do indeed effortfully try to develop a model of what they're impressed by, and then use that model when talking to them. And I tend to succeed! And it's not all that hard! The most obvious strategy tends to work (i.e., go with what has impressed them in the past, or what they say would be impressive, or what impresses similar people). I don't really see any aspect of human nature that is working to make it hard for me to impress someone, like by a person randomly changing what they find impressive. Do you? Are there better examples?

2Viliam6y

I have low confidence debating this, because it seems to me like many things could be explained in various ways. For example, I agree that certain predictability is needed to prevent people from messing with you. On the other hand, certain uncertainty is needed, too -- if people know exactly when you would snap and start crushing them, they will go 5% below the line; but if the exact line depends on what you had for breakfast today, they will be more careful about getting too close to it.

Steve Byrnes’s Shortform

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Steve Byrnes’s Shortform

5

Ω 2