Vision is a 'Reflex' 45
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."
Looking at prOn... (Score:5, Funny)
Honest, Dear (Score:4, Funny)
Somehow that never works.
To simplify (Score:3, Informative)
How well this fits into modern life and jury trials is another issue.
Syntax vs Semantics (Score:5, Interesting)
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...
Re:Syntax vs Semantics (Score:5, Interesting)
Now do the same to a human. You might
The writeup says that the conventional explanation involves (something like) colour bleed within the neural system to get the effect; for which there is no direct evidence and no explanation for
The idea that there might be some evolved preprocessing mechanism at the fundament of our vision which prevents us from seeing like cameras (as opposed to simple 'mechanical flaws') is actually recent and controversial (theres a chapter on exactly this in The Blank Slate [mit.edu] thats worth reading), so I don't think it quite qualifies as 'banal'.
The Duke guys don't seem to be quite saying that we see the past at a macro level (leaves, trees, sheep) so much as at a micro level. Something is translating raw colour info into shape, distance and colour
Anyway, thats what I thought they were saying, I could have completely misunderstood. It would be more convincing if they could construct a computer model from their ideas that had the same vision defects we do.
-Baz
Re:Syntax vs Semantics (Score:3, Informative)
Frequently we don't see two instances of the same wavelengths of light as the same colour, but that's because there are obvious evolutionary advantages of not seeing the same 'colour' as the same colour quale (the 'mental image of the colour'). Such as when there are red berries amongst green leaves, where it is advantageous for the red to look more red and the green to look more green, or such as edge detection, where if you have alternating strips of light and dark the light seems lighter and the dark seems darker where they meet, emphasising the edge.
I assumed that everyone had accepted that these were the products of evolution, and didn't think that illusions were illusions in a pejorative sense (i.e. not defects) - but it seems like these guys are presenting this as something new and exciting, and I just can't see how...
White balance. (Score:3, Interesting)
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.
'the eye isn't a simple camera' (Score:3, Interesting)
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.
Re:'the eye isn't a simple camera' (Score:1)
Jaysyn
Re:'the eye isn't a simple camera' (Score:1)
Heh... (Score:1)
FWIW, the end-user experience is the groggy, confused state you have when waking from a fever. Edge-detection and pattern-recognition goes haywire; perspective (in the sense of distance/size) goes totally out of whack.
In my case, the classic psychedelics (one starts with L) actually seem to enhance my visual acuity, but the constant stimulation they engender eventually results in some filling in of the 'boring spots' where there's not much of note.. or perhaps it's simply a matter of the reflex response being 'accellerated' such that all the pathways of association for an input get triggered at once.
Re:Syntax vs Semantics (Score:1)
I disagree. Their claim, basically that the perception of visual stimuli is more like a reflex--an autonomic action--than a higher order analytical function, is hardly banal. It goes against almost all currently accepted thought on the subject.
I also don't think they were stating that we don't get any new ideas from visual stimuli--that would be obviously false, as you say. Just that how we make sense of that stimuli has to do with what we have to draw on--our past experience, personal or evolutionary.
Re:Syntax vs Semantics (Score:2)
That is to say, we know that there are basic, anatomical reasons for visual illusions.
And of course how we make sense of stimuli has to do with past experience, again, I can't see how this is anything more than banal. They can't seriously think it's a new idea that how we see is the product of past visual experiences. Only a creationist could think that it wasn't...
Re:Syntax vs Semantics (Score:3, Insightful)
It isn't all semantics or syntax (Score:2, Interesting)
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.
Re:It isn't all semantics or syntax (Score:2)
I'm going to have to disagree strongly with one thing you say, however:
"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."
The reason I'd deny this is that the brain isn't banking on anything. This would be a weird sort of functional explanation that just doesn't hold up. It isn't that at some time your brain / genes / evolution thought 'Hey, maybe I'll have past experiences again / similar experiences in the future'. What actually happens is that experiences happened to it, and some animals had a freak mutation which meant that they were better at reacting to this experience, for example because they were especially good at seeing red berries amongst green leave, and so this gene survived.
To characterise this as being in a state now where the brain 'thinks' 'things will occur that are similar to those that have occurred in the past' gets it totally the wrong way round - it's simply that those things that have been up for testing in the past we have developed tests for. It would be taking a hideously bad test population to look at those things which we perceive in some interesting way and think 'Wow, it's odd,
Re:It isn't all semantics or syntax (Score:1)
See, the difference here is the Duke researchers, and what I write here, is descriptive. What the brain may be doing is the equivalent of a statistical analysis, where the express purpose is to link raw sensory input into a perceptual quality. However, the actual description of thought eludes researchers at the moment. I can tell you in detail how the peripheral olfactory system responds to volatile chemical compounds. Is any of this mechanistic description good for telling us how we perceive odors, or at what point neuronal activity turns into a thought? One short circuit to this argument is that mechanism is not quite the same as a functional analysis. If we can identify some machine as a combustion engine, can we say with certainty that the engine belongs to a car or to a plane?
Another point is that you confuse evolution of a system (and system effects) with how the detail actually plays out. Your evolution example is not quite proper, since you assume that the details are the goal, and not the system to handle change. It isn't that the brain necessarily needs to know what it has seen before; it's just that the brain (i.e. neurons) can organize their activity in such a way that subsequent exposure to the same stimulus evokes activity in that same set of neurons. In the hippocampus (in rats, where this research was done), there are actually neurons that are sensitive to location. That's right, there are a group of neurons where, if a rat is let loose in a novel or an old environment, activity from cells are "mapped" to locations in that physical field. That is to say, a few neurons respond when the animal is at a particular point in that testing field. How do these neurons "know" when to fire? Is the rat consciously aware of its absolute location in that field? We still don't know (this research was done about 10 years ago.) Don't make the mistake of misunderstanding the mechanistic description for the phenomenon we call "thinking." When those researchers write about a "reflex", what they mean is that, neuron ensembles respond to a stimulus according to a "best-fit" manner. Stimuli with similar attributes (for example, then entire set of faces) evoke activity in neurons that have similar responses to those stimuli. In that sense, neural activity in the visual system is somewhat like a reflex: hitting the same spot (or showing rectangles differing only by color, or by size) will likely evoke the knee-jerk reflex (or the neurons that respond to rectangles will respond to all those slightly differing rectangles.)
Sometimes, scientists or the press get out of hand, and they start using non-specific words, or words with loaded meanings (but which refer to specific concepts in neuroscience). Or, genuine misunderstandings occur where laymen think a piece of research says something much more that what research usually says (trust me, this happens a lot. I explain mechanisms of smell, for instance, and everyone will start talking about how some smells evoke wonderful memories and must therefore be a primal, ur-sense... )
The problem you may have with what the researchers describe is that you may not see where emergence can occur. I've said that the brain (neurons, actually) adapts their activity based on the input. It does so by altering the connections (synapses) between neurons. Sometimes, this means causing the cell to "fire" when a particular set of synapses are active; sometimes it means the opposite. But only in this way do we mean that the system "remembers" and "knows" what has happened before, without the self (or ego, or id) having had conscious recognition thereof. Those researchers were writing about the details of how neurons respond; yes, ideally, this would also mean that the brain must be conscious of such changes. Once again, by documenting such small-scale, but important changes, we may get an idea of how the brain actually does thinking. As for the example I used, I only mean to address the common basis of the machinery. When I wrote about the brain banking on consistent, physical phenomena, of course I only meant that in an aggregate, general descriptive sense. The brain doesn't know what it is going to see. The system has evolved, however, to handle physical stimuli in a certain way that seems consistent across many species of animals.
Re:pr0n? (Score:1)
There was an artile like this (Score:4, Interesting)
Re:There was an artile like this (Score:2)
I could have told them that! (Score:3, Insightful)
I could have told them that what you perceive as being there is based on your previous experience as opposed to what is actually there. The data from your eyes is just far too noisy, and my brain has guessed wrong often enough that its become obvious that what I was seeing was based on previous experience. By the way, hearing works the same way. Calling it a reflex, however doesn't seem right.
I doubt this will revolutionize anything... (Score:5, Funny)
Re:I doubt this will revolutionize anything... (Score:2)
That's a reflex too :). (Score:2)
Rather similar to the blink reflex, where you take quick action to protect your sight from blink tags on a webpage.
Seems like common sense to me (Score:3, Interesting)
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.
Re:Seems like common sense to me (Score:3, Informative)
The article also misrepresented some of the research that has gone on in the past. Visual circuits have been traced and analyzed in an effort to learn how the brain sees, not what it sees (which is what their theory is really about). Researchers want to know how the brain is able to detect motion against a noisy background, how people are able to represent 3-D objects in their heads, how the brain assembles thousands of visual cues into a coherent representation of the world. (Some brain injuries disrupt these functions -- there are people who cannot see motion - moving objects are percieved as stationary objects that jump around discontinuously - some people are not able to construct an image of everything that their eyes detect - they can only see one or two distinct objects at a time). The observation that vision is a kind of reflex does not even begin to answer questions about how the visual system works. I don't see how they can call it a theory of vision if it doesn't offer any explanation for fundamental problems that visual systems must solve.
Also the comment about detecting the source of sounds is incorrect. The neural circuit that takes care of that has been known for a long time. It localizes sounds by comparing phase differences between sounds arriving at each ear. In fact, it has even been demonstrated that the circuit trains itself to do this task (a great example of how Hebbian learning works).
I'll give them the benefit of the doubt and assume that the person who wrote the article didn't understand a bit of their theory.
Re:Seems like common sense to me (Score:2)
That's not always true. For example, you can be out in the woods and hear a sound but can't tell if it's a Cougar or a human baby crying. Or when you hear the neighbor's dog and can't tell if it's barking or telling you to quit touching yourself and go punish someone.
;^)
Duke Magazine need a course in perception (Score:3, Informative)
Re:Duke Magazine need a course in perception (Score:1)
This article is bullshit. (Score:3, Informative)
Compare this to an illusion that actualy passes this test: checkershadow [mit.edu]
The question is why make a bogus illusion when a good ones exist? NIH? (Or perhaps they don't want to support MIT?) Is all their "research" of this quality?
The reason why the brain confuses colors and such is because it quite sensibly corrects for shadows. It very sophisticatedly determines the light source, and compensates for it. Why is that so hard to grasp?
Re:This article is bullshit. (Score:2, Insightful)
This seems partly their point. Millions of years of evolution and decades of personal development lead to this sophisticated compensation mechanism. Which makes assumptions which turn out to incorrect, and can be fooled. The light hitting the eye is ambiguous, the brain applies assumptions that in the past worked, but fails when exposed to illusions of this sort.
Re:This article is bullshit. (Score:1)
The assumptions are indeed correct here in the real world. It's not often you walk into a room with fake shadows drawn everywhere.
And the idea that the brain fixes what the eyes see is nothing new. There is an easy to do experiment where you wear lenses that invert the image your eyes see. After a week or so you'll wake up one day and realize that the world is right-side-up again.
And once again, an illusion is only an illusion if it is really an illusion and not falsified.
Re:This article is bullshit. (Score:2)
Re:This article is bullshit. (Score:1)
Some of their other examples are also flawed which I won't get into because I've got better things to do.
Save yourself some time, go to the MIT site and read something worthwhile.
"Gestalt" is nothing new. (Score:2)
n. pl. gestalts or gestalten (-shtältn, -shtôltn, -stältn, -stôltn)
A physical, biological, psychological, or symbolic configuration or pattern of elements so unified as a whole that its properties cannot be derived from a simple summation of its parts.
[German, shape, from Middle High German, from past participle of stellen, to place, from Old High German. See stel- in Indo-European Roots.]
Source: The American Heritage® Dictionary of the English Language, Fourth Edition
Further reading: Francis Crick (Score:2)
Yes, this is the same guy that co-discovered DNA.
"Reflex" is the wrong word (Score:2, Informative)
This still doesn't explain... (Score:1)
What's new here (Score:2)