Rachael (woodpijn) wrote,

Top-down and bottom-up processing

A couple of Scott Alexander's latest posts (and some of his earlier ones) relate to the balance between how much you rely on incoming sensory information versus priors, or bottom-up versus top-down processing. (This is not as simplistic as saying "some people won't change their pre-existing beliefs even when confronted with contradictory evidence." Top-down processing is a vital component of anyone's cognition. It's what allows you to see some unconnected pieces of dog through the gaps in a fence and effortlessly perceive a whole dog, or to hear a cashier's shout distorted by a noisy supermarket into "ex ease" and know it's overwhelmingly likely to be "next please" and not "sex cheese". Everyone needs to give some weight to their priors and some weight to the new incoming information; it's just that some people in some situations err more in one direction than the other.) The balance between the two types of processing has implications for all sorts of things in psychology, like autism, schizophrenia, and depression.

I think this has also given me a new insight into the iNtuition–Sensing axis of the Myers-Briggs Type Indicator.

(Brief digression about the MBTI: I'm not saying it has any particular objective validity (the Big Five is better for that, as it's supported by factor analysis), but pretty much any arbitrary personality classification system has some value, even Hogwarts houses, in that it provides a useful shorthand and shared vocabulary for talking about certain aspects of personality variation. Alex and I also found the MBTI helpful when we were at a church where we felt unhappy and alienated: it helped us understand that we weren't Wrong and the church wasn't Wrong, but the church was very F on the Thinking–Feeling axis and we were very T.)

I've always been a bit unsure about what the N–S axis represents. I thought maybe N meant "rich inner life, head in the clouds, comfortable with abstraction" and S meant "more concerned with concrete practical realities", and on that axis I'm more N. But now I'm wondering if another way of looking at the N–S axis is that it captures the the tradeoff space between top-down and bottom-up processing: how much you rely on new incoming sensory information versus the "intuition" of your priors. Under this interpretation, I'm very strongly S.

This is what makes me good at maths and programming and proofreading: I see the detail of what's actually there rather than what I expected to see. (Although I'm not completely immune to seeing what I expected to see: another pet hobby of Scott Alexander's is to sneak instances of repeated "the the" into his essays about top-down processing and seeing if anyone notices them, and even though I'm pretty good at spotting other typos, that one doesn't leap out at me in the same way. Luckily for my actual proofreading work, Word and Google Docs are good at spotting repeated words. Did you spot the "the the" I put in earlier in this post?)

It's also what makes me bad at engaging properly with Bible studies: I get hung up on the one point in the whole passage that says something that doesn't seem to make sense, and to me it feels like other people are spouting obvious platitudes while ignoring the elephant in the room, while to them it probably feels like I'm missing the forest for the trees and obsessing over a minor irrelevant detail. (The one time I ever led a study myself, it was on James 2, and I spent most of my preparation time trying to figure out whether there was any sensible explanation for the glaring inconsistency in verse 18 or whether it was just an error: where James, who is making an argument that faith without deeds is not enough and deeds are also needed, has his opponent saying "You have faith; I have deeds", rather than the other way round, and then answers them "Show me your faith without deeds, and I will show you my faith by my deeds." It turned out the others in the study had literally not noticed the inversion and had read it as if it said "You have deeds; I have faith", and even when I pointed it out, it didn't seem to bother them or have any effect on the high-level message they got from the passage, which was just that faith and deeds are both important.)

I'm also incapable of getting so absorbed in an activity that I forget to eat. I like the idea of being an abstract ethereal being of pure intellect who's untroubled by such base concerns as food, but in practice I can't pull it off, because the immediate sensory data of hunger is too salient for me and can't be overridden by mental focus on an activity.

Also, in the same way as Scott describes depressed people viewing all their expreiences through a depressive lens and therefore not being able to let neutral or positive experiences update their long-term depressive priors, I wonder if my "always like this fallacy" is something like the inverse of that: I over-update on my current experience, whether positive or negative, and feel like my whole life has always been like that and always will be. This seems to fit with over-weighting current incoming sensory information (using "sensory" in the same slightly broader way that Scott uses it) at the expense of priors.
Tags: christianity, fallacies, programming, proofreading, psychology, scott alexander

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