Here is a fascinating article from The New Yorker, mostly about itching but not just.  Here is my favorite part:

A new scientific understanding of perception has emerged in the past few decades, and it has overturned classical, centuries-long beliefs about how our brains work–though it has apparently not penetrated the medical world yet. The old understanding of perception is what neuroscientists call “the naïve view,” and it is the view that most people, in or out of medicine, still have. We’re inclined to think that people normally perceive things in the world directly. We believe that the hardness of a rock, the coldness of an ice cube, the itchiness of a sweater are picked up by our nerve endings, transmitted through the spinal cord like a message through a wire, and decoded by the brain.

…Yet, as scientists set about analyzing the signals, they found them to be radically impoverished. Suppose someone is viewing a tree in a clearing. Given simply the transmissions along the optic nerve from the light entering the eye, one would not be able to reconstruct the three-dimensionality, or the distance, or the detail of the bark–attributes that we perceive instantly.

…The images in our mind are extraordinarily rich. We can tell if something is liquid or solid, heavy or light, dead or alive. But the information we work from is poor–a distorted, two-dimensional transmission with entire spots missing. So the mind fills in most of the picture. You can get a sense of this from brain-anatomy studies. If visual sensations were primarily received rather than constructed by the brain, you’d expect that most of the fibres going to the brain’s primary visual cortex would come from the retina. Instead, scientists have found that only twenty per cent do; eighty per cent come downward from regions of the brain governing functions like memory. Richard Gregory, a prominent British neuropsychologist, estimates that visual perception is more than ninety per cent memory and less than ten per cent sensory nerve signals.

And sorry, readers, for shouting in the header; sometimes I get carried away.  By the way, don’t let defenders of naive realism tell you that any attempt to contradict it is self-refuting.  Science proceeds in pieces, cross-tested in various ways, and the sum total of those pieces can revise our understanding away from naive realism without producing self-contradiction.


I wonder what the balance between perception/processing is like for other animals.

This makes me wonder about how much we take in for reading since unlike looking at a tree in a clearing we are presumably looking at unique combinations of visual symbols where the uniqueness matters.

We do tend to only read the first and last letters of a word and the size.

Sounds like Hayek in the book The Sensory Order or in the article "The Primacy of the Abstract." I never knew Bryan Caplan was a naive realist.

Wasn't this largely what Daniel Gilbert's book was talking about?

Not really a new insight. Here is William James from 1892:

"Perception is of Definite and Probable Things--The chief cerebral conditions of perception are old paths of association radiating from the sense-impression. If a certain impression be strongly associated with the attributes of a certain thing, that thing is almost sure to be perceived when we get the impression. Examples of such things would be familiar people, places, etc., which we recognize and name at a glance."

There are many other accounts of perception 'filling in' features that aren't actually present in the current input (because the features are occluded, for example). We can recognize an object on the basis of a subset of the features, fill the rest in from memory, and not be certain what was actually in the image and what was 'filled in'. This is just not a new insight.

Very cool. I suppose that it kind of makes sense. Perhaps it's more economical to process the information from the brain than externally. Throw evolution into the mix and brains that can't process effectively get selected out. So the external signals are just enough for the brain to be effective.

Someone forgot to turn italics off. Caplan relies far too much on intuition. That's why he still believes in objective morality.

This sounds like a straw man to me. introduce me to the medical people who believe we "perceive" 3d directly, or that what we get from our senses is not a noisy, limited view that the brain must interpret and reconstruct.

I should point out that I am not a naive realist, but a thoroughgoing Batesonian.

This is old hat and it does not refute naive realism. I mean, really - that our inputs are impoverished and that our perception is largely a matter of guesswork? This is news to you? I recommend that you read some actual defense of naive realism if you're interested. And before you go and pronounce Bishop Berkeley as somehow vindicated, please, get clear on what he's saying.

Interesting. Perhaps this is part of the reason why existing image processing systems are still so weak in comparison to human visual ability? Perhaps we have modelled the actual "vision" part quite well already, and we won't get better results until we incorporate memory and other brain-internal resources.

There is a parallel to computational linguistics, where we had to finally admit that language cannot be fully modelled just by manipulating strings of words.

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It is enlightening!

There is a parallel to computational linguistics, where we had to finally admit that language cannot be fully modelled just by manipulating strings of words.

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