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Vision is a 'Reflex'
kernkopje writes "A recently publicized book by two neurobiologists at Duke University introduces an interesting emperical theory on vision. Rather than postulating a visual system that generates a picture of what actually exists in front of the viewer, they theorize that evolution, as well as life experience, has created a visual system in which perceptions represent what a given visual stimulus has typically signified in the past. Admiring the view from a high building, staring at a beautiful woman, shapes, colors, textures, it's basically all the same knee-jerk response...
The news release is here, read more about the concept here. Their lab work & results can be found here."
Whilst this article is interesting, and raises some interesting points, they seem to come to some very radical conclusions, based on what can only be called a mistaken belief that vision is 'about' something. They claim that rather than perceiving what is out there, we perceive what we've been trained to see, by past experience individually and of the species.
Well, we can take this two ways. We could say that we've grown eyes and a complete visual system purely based on previous stimuli, in which case it's obvious that new stimuli will only be interpreted in terms of past stimuli. Or we can say that we currently have an apparatus, and despite the fact that something we're immediately seeing might be ambiguous and look like something we've previously seen we could have further sense data that tell us that it isn't what we'd seen before - so what looks like a famous statue could be revealed to just be a photograph of a famous statue when you move around and see that it doesn't change corresponding to how it should.
But either of these interpretations - the past-centric and future-centric ones - are just that, interpretations. They still aren't 'about' anything.
What this article seems to be claiming is that anything you're currently seeing is actually 'about' things in the past, but clearly this isn't true. Vision isn't 'about' anything. When you have a robot with sensors you don't say that when they 'see' an object in their way what they're seeing is 'about' their programming, so they're not actually seeing anything in the present.
Sorry, I'm not putting this very well. Basically I'm trying to say that either their claim is banal - the obvious fact that our eyes are only capable of creating objects in our 'minds' based on things that have been saliant in the past (such as emphasising red objects - i.e. berries - in a green field - i.e. leaves - more that they actually contrast), since obviously our visual system has evolved based on what has been saliant in the past. Or they are making an incorrect claim that current vision is just 'seeing the past' because we don't actually get new ideas from our visual fields, we just try to fit it into previous sets of sense data. The reason that this must be incorrect is that past sense data is no more 'real' no more 'seeing actual objects' than current sense data. So if I see an apple now, it isn't fair to say I only know it's an apple because I've seen apples before because the only sense in which I've seen apples before is the sense in which I'm currently seeing apples. There isn't a 'good old days' when we really saw things, and which we're just reminding ourselves of every time we try to see again...
in Discover, or scientific american a while back. It was a bout a man who had been given sight back after losing it as an infant. He went form being blind, to having decent vison at teh age of 40? or so. IT was fascinating reading. Depth perception for him was something he had to think about, optical illusions didnt work. Catching a ball was a new experience. He learned to ski while blind, so skiing with vision was actually harder in ways, he had to lear to interpret what his eyes were telling him, versus what his legs were telling him.
All Troll + "offtopic" mods are meta moderated as "Unfair", because you abused the system.
You missed the forest for the trees. Consider the following experiment: Someone draws a few lines on a canvas. Ask hundreds, or thousands of people to trace the lines with their fingers, or a stick. Eventually, you'll be left with a canvas with furrows where the drawn lines were. The basic, and banal, interpretation is that those people tested perceived the lines the same way. If the sample size is large enough, and properly random, one can make a statistical inference about the population (that is, all individuals contained in the human-group.)
Of course, this experiment is banal, for all we do conclude from it is that, for whatever individualistic, subjective perceptions about the world, all humans (and let's face it, it's most likely all other vision enabled animals) have a common mechanism by which those percepts are created. You've ignored that when the brain creates a visual image, it must have trained before-hand. The training likely continues throughout life, and, while images are not always created de novo, it may enable the brain to make do with an image that results from a combination of stored percepts and new information about the visual environment.
How do we know where such percepts are stored and generated? In the temporal and occipital cortices. But that doesn't say anything about the mechanism by which visual information storage, retrieval, recombination, and generation happen. As it is, the significance of what the Duke researchers suggest (and they aren't the only ones) is that the visual system banks Bayesian statistical sorting to select the likeliest base percept based on the information at hand. Such an algorithm, if you will, only occurs after a training period (otherwise, where would all those percepts come from?) The brain then is actually banking on the replicability of natural phenomena: light striking objects and reflecting a particular set of wavelengths consistently. Photon scatter, absorption, and transmittance properties are conserved by the same materials. Only in such a world is it useful for the brain to assign percepts called color and shapes to these sensations. While these assignments may in fact be arbitrary (for whatever reason, blue looks blue -- but what if blue looked red? Does it matter?), so long as the assignment remains consistent, the brain can confidently assign and sort incoming raw information into perceptions.
To say that science cannot contribute to our understanding of subjective perception is inane. I can identify men who are color-blind, and women who perceive four base colors rather than the three everyone else perceives. How? Well, don't forget, that the actual way something looks in your mind's eye is irrelevant: the only condition is that you see things your way, consistently. Testing for subjective color perception is as follows. Take a red background and write a number in green (or vice-versa). Show it to a person whom you think is color blind (red-green colorblindness happens to be the most frequent form in men.) A colorblind person will not be able to tell you what number you've written. It's as simple as that. He simply cannot distinguish reds from greens. Notice I never said that he sees reds as greens or greens as reds. It doesn't matter. We've identified that he cannot distinguish between the two. As it turns out, there's a molecular basis for this: he has a misfunctioning red-green receptor protein. Now, what is most interesting is that this protein is X-linked; men are more frequently colorblind because they only receive one copy, on the X chromosome. Since they are male, they must have a Y chromosome, given by their fathers. Females are more commonly carriers, and they'll need two busted copies before they become colorblind. So, how do these women perceive color, then, if they have 2 normal color receptors, and then one good red-green receptor and one bad red-green receptor? It turns out that they functionally have four photoreceptors; they can consistently distinguish colors that those of us with 3 photoreceptors cannot. They consistently detect the differences, in the same way. Sure, one may never know how it is to see so many colors, but we can actually identify those people that do. This isn't just syntax and semantics, people.
A second example: Do you think you have sharp vision? Do you think your peripheral vision is as good as your central vision? I can tell you that no, your peripheral vision sucks, and it doesn't take too much to show anyone. Look at a book or newspaper. Focus on a word. How many words can you perceive clearly around that one word? It won't be too many. The density of photoreceptor changes at different locations in the eye. The fovea has the highest photoreceptor density, and you can make up all sorts of stories about how density of sensors lead to sharpness of "picture." It also happens that only this foveal region (probably about 1/50 of the entire area of the retina) contains color receptors. That's right, if you focus on one spot, you'll realize that you can perceive colors in your peripheral vision. But you aren't really getting real-time color information - you have no color sensors there! Your brain must be creating the perception of color -- perhaps in the statistical way the Duke researchers write about in their book. Not only that, the periphery doesn't provide as sharp a picture either (and if you believe the results of the word-view test, it doesn't seem like you have to go far from the fovea before your brain needs to "fill-in".)
No scientist denies that new information cannot be received by the brain. After all, and especially if the nervous system is one big Bayesian statiscal inference machine, the brain will need to see new things, and assign the probabilities accordingly. The actual mechanism is still being researched. There is a place for syntax and semantics, but at the level of biology, there is only one mechanism that matters: the one the animal uses.
Now let's say you are talking to someone for the very first time. Do you instantly recognize their voice? Of course not, you've never heard it before. Do you recognize it as a human voice? Yes you do, unless they've had a trachiotomy or something. The brain of course makes this determination and tells you that it's a person not a dog or a cat, etc.. Now the next time you speak with this person, the voice may be more familiar. Each successive time you speak with them, your chances of accurately identifying the voice without having to think about it go up.
Certainly some aspects of our visual system are inherited, the fact that we can distinguish between red and green even thought there is little contrast in their brightness. Or the fact that our vision is best suited to naturally lighted (read sunlight) situations. These are basic adaptations of our visual system, both sensors and processing, to the environment in which it evolved.
What the article seems to be saying is that all less basic aspects of our visual system are learned. For example, you may not know what type of car is driving in front of you in traffic, however after you get the latest Road & Track and read about model X, you begin to recognize the car without having to think about it. I'm not saying the article is banal, I'm simply saying that what it talks about seems like common sense. That said, I think it is important to scientifically explore things that seem like common sense, because if we were to simply dismiss a line of inquiry because the answer seemed like common sense, we would often miss out on some very interesting discoveries.
Well, it kinda is. It's the bits that do the processing that arn't.
Suffering from frequent migrains and having some other bad seritonine based illnesses I can tell you what it's like to have diffency or enhancement in processing what you see.
When you see words/letters your brain see's words and letters, not a bitmap.
How do I know this, well sometimes I have problems being able to see shapes properly, and have to consesly work out what things are.
Patterns are picked out as textures for the shape, sometimes I see the patterns 'waving' around and blury, it's very hard to tell what the shape is.
Speed and motioned is also determined using some of the elements, often when a pattern becomes wavey it feels kinda like the floor is moving, and my sense of distanse goes tits up.
Well, it's all fun, and I can get by, it just takes a little more concentration now and again.
Oh and did I say it's fun, like being on Acid for free.
thank God the internet isn't a human right.
The colour thing is useful for humans - coz it's good to perceive how ripe a fruit is even if the lighting changes.
It's probably similar to automatic white balancing which you have in many modern colour cameras. But the reason for that is kind of circular - most pictures are viewed by humans. If a computer ever needed to guess something's objective colour under subjective light it'll be useful.
As for the flaws/bugs/illusions etc, hey that's evolution for you, perspective, autocontrast/balance. If I want to complain about anything, I'd complain about the damn blind spot practically next the the fovea. Octopuses don't have such blind spots.