hfavr@mtuxo.UUCP (a.reed) (07/15/86)
I have not read Kelley's book, but as a psychologist I am familiar with Gibson's "environmental" (or "ecological") theory of perception. In the standard contemporary conceptualization of perception, from which Gibson dissented, the input to the perceptual process is thought to be the sensory impression; for example, in visual perception, the pattern of retinal stimulation. According to the standard theory, the task of the perceptual system is to derive, from that pattern, a representation whose features are analogous to those features of the environment which originally caused the retinal pattern. If the perceptual system is thought of as physically limited to the eye and the brain, the standard view is close to being a logical necessity. It is from this conceptualization that Gibson dissented. In Gibson's view, the perceptual system is not limited to the confines of the organism, but extends into the environment. In the course of its evolution, the organism has assimilated physical mechanisms present in its natural environment to function as integral parts of its perceptual system. Thus, the perceptual processes implemented in the eye and the brain have evolved to function as the back-end of an integral process of perception that begins at the perceived object. In this view, the natural light sources present in the environment, the reflective properties of the surfaces of objects, and the optical characteristics of the atmosphere are as much a part of the human perceptual system as the eyes and the brain. Thus, the retinal stimulation pattern is not the input to perception, but rather an internal stage in the process. The input to the perceptual process is the object itself; the output is the organism's awareness of the object. The information contained in this awareness is the original, and not a re- (or transformed), presentation of the object to consciousness. According to Gibson, the experimental psychologist's laboratory use of two-dimensional representations, tachistoscopic stimuli, illusions, and other materials that were not part of the ecological environment in which the human perceptual system evolved, amounts to studying the human perceptual system with some of its key parts removed. This is rather like trying to find out how a computer works after pulling out some of its chips, or deducing normal physiology from the results of the surgical removal of organs. To yield valid information, the results of such experiments must be interpreted with special attention to the fact that one is not studying an intact or properly functioning system. Adam Reed (ihnp4!npois!adam)
colonel@sunybcs.UUCP (07/16/86)
> In Gibson's view, the perceptual system is not limited to the confines > of the organism, but extends into the environment. In the course of its > evolution, the organism has assimilated physical mechanisms present in > its natural environment to function as integral parts of its perceptual > system. Thus, the perceptual processes implemented in the eye and the > brain have evolved to function as the back-end of an integral process of > perception that begins at the perceived object. A worthwhile way of looking at perception. I find it ironic that many (most?) cog-psycholgists' experiments in perception use CRTs to display "objects." Not only does this practice effectively divorce sight from the other senses, it also enforces a deviant mode of perception on the subject. (To perceive an "object" on a flat image, the subject must focus _behind_ the image. Most literate people are unaware of their habit of doing this.) Self-respecting people don't care to peep at their reflections in unexpected mirrors. --L. P. Smith -- Col. G. L. Sicherman UU: ...{rocksvax|decvax}!sunybcs!colonel CS: colonel@buffalo-cs BI: csdsicher@sunyabva
ln63szf@sdcc3.ucsd.EDU (Rick Frey) (07/21/86)
I haven't read Kelley's book either, but I'm pretty familiar with Gibson and a few of the major problems in his theory, most of which you present. In article <1782@mtuxo.UUCP>, hfavr@mtuxo.UUCP (a.reed) writes: > In the > standard contemporary conceptualization of perception, from which Gibson > dissented, the input to the perceptual process is thought to be the > sensory impression; for example, in visual perception, the pattern of > retinal stimulation. Here you start off a bit unclear. When you talk about input to the perceptual process, to what are you referring? The signals that will travel down the optic nerve? What will end up in the occipital cortex? Area 17? You need to be more specific, as did Gibson. > If the perceptual system is > thought of as physically limited to the eye and the brain, the standard > view is close to being a logical necessity. It is from this > conceptualization that Gibson dissented. A distinction that most physiological psychologists won't make. All (all good) PS's know that at some point, information about the regularities of the external world need to be used in order to make sense out of visual stimuli. Helmholz, Rock and some others say that this information comes in the form of conscious structuring of visual information whereas Ramachandran and some others say that the regularities of the external world are hard wired into the perceptual features of the system. Thus the Phi phenomenon (illusory motion) isn't do to a conscious realization that objects blinking between two locations might be moving between them, it's do to a hardwired understanding that in the real world, objects have to travel through paths to get to another location; blinking is impossible. > In Gibson's view, the perceptual system is not limited to the confines > of the organism, but extends into the environment. In the course of its > evolution, the organism has assimilated physical mechanisms present in > its natural environment to function as integral parts of its perceptual > system. This isn't only Gibson's idea. I'm not sure on who came up with it first, but he certainly isn't the sole posessor of the idea. > In this view, the > natural light sources present in the environment, the reflective > properties of the surfaces of objects, and the optical characteristics > of the atmosphere are as much a part of the human perceptual system as > the eyes and the brain. Thus, the retinal stimulation pattern is not the > input to perception, but rather an internal stage in the process. The > input to the perceptual process is the object itself; Gibson's major mistake. This simply isn't true. Obviously it has to be the light that makes it to the organism. If no light reaches the organism, then there's no perception. Period. Unless the organism *perceives* the object, it doesn't exist to the perceiver. Perception starts once there is something to perceive, and that only can begin when perceptual information about the object makes its way to the perceiver. > the output is > organism's awareness of the object. The information contained in this > awareness is the original, and not a re- (or transformed), presentation > of the object to consciousness. Information contained in awareness? This is somewhat Gibsonian in that he uses words that have no clear definitions, but I don't think even he would quite say this. What is awareness? What stage of processing are you referring to? Aside from the actual collection of excited and inhibited receptors at the retinal level, *all* perception is transfor- mation. Sorry, no homunculae. (sp??) > According to Gibson, the experimental psychologist's laboratory use of > two-dimensional representations, tachistoscopic stimuli, illusions, and > other materials that were not part of the ecological environment in > which the human perceptual system evolved, amounts to studying the human > perceptual system with some of its key parts removed. In some cases, this is a valid claim of Gibson's, but his whole theory rests on it and it isn't 100% true. He'd love to have us believe that the external world is rich in information and that perception is an easy task of picking out of the multitude of cues available. That's simply not true. Experimental psychologists aren't blind to this criticism, and far too many experiments have been done that don't fall under Gibson's criticisms of artificiality. Perception developed under situations where the available information was far from over-abundant. Without this over-abundance of information, Gibson's ideas start falling apart. > This is rather like trying to find out how a computer works after > pulling out some of its chips, This is a purely Gibsonian analogy, and accordigly isn't accurate. Studying perception in the laboratory removes nothing from the perceptual machiney. It removes perceptual information that Gibson says has to be there, which, I'm sorry, but you don't get to tell nature "Make sure all the information I need is there or I'm going to screw up." Adaptivity would seem to indicate that an organism that could still make the best judgement with the least information would be the most fit to survive. Perception developed in a piecemeal fashion such that there wasn't an overabundance of information at various stages in the development. So where did this 'perceptual laziness' come into play? You try finding a small tree frog in a huge tree. The whole idea of an overabundance of perceptual information might apply to recognizing people's faces, but it has no basis in the reality of where and how perception developed. > To yield valid information, the results of > such experiments must be interpreted with special attention to the fact > that one is not studying an intact or properly functioning system. True, but with the modified analogy, if you put a number into the computer and get something out, if the machinery is the same in all states (which in reality, it is) you get information any time you put something in and get something out. Don't throw it away because it isn't an exact analogy to the natural environment. You do need to be careful in interpretting what you find, but the answer isn't to say that is's all artificial and the only real perception stems from objects in the natural world. Rick Frey (...ihnp4!sdcsvax!sdcc3!ln63szf) (ln63szf%sdcc3@sdcsvax.UCSD.EDU or .ARPA) (I've been switched temporarily to sdcc3, NOT sdcc7)
toddo@uhmanoa.UUCP (Todd Ogasawara) (07/23/86)
In article <3483@sdcc3.ucsd.EDU> ln63szf@sdcc3.ucsd.EDU (Rick Frey) writes: >> In this view, the >> natural light sources present in the environment, the reflective >> properties of the surfaces of objects, and the optical characteristics >> of the atmosphere are as much a part of the human perceptual system as >> the eyes and the brain. Thus, the retinal stimulation pattern is not the >> input to perception, but rather an internal stage in the process. The >> input to the perceptual process is the object itself; > >Gibson's major mistake. This simply isn't true. Obviously it has to be >the light that makes it to the organism. If no light reaches the >organism, then there's no perception. Period. Unless the organism >*perceives* the object, it doesn't exist to the perceiver. Perception >starts once there is something to perceive, and that only can begin when >perceptual information about the object makes its way to the perceiver. > [before I begin, let me say that I agree with most of what Rick has to say] Visual perception and interpretation is of course based on light striking the retina. However, reflected light from from an object is not really the only way to perceive objects. The best example of this is the filling in process that takes place to prevent our "perceiving" the blind spot of each eye. The optic nerves collect at a point of the retina where there is no receptors. Yet we do not perceive a black hole in our visual field. You might say well this is because the corresponding input from the other eye covers up. Simple to test and disprove this: close one eye. Still no black hole in visual space. The black hole is simply assumed to be there by the brain and is "filled-in". Another example is my original dissertation topic: subjective contours. Artists have long known that you can "suggest" contours and edges by manipulating the placement of black areas. There are ways to place lines and black areas to force the visual system to perceive whole and sometimes complex objects (curved, etc.) For some good illustrations, and an easy to find reference, check out: Kanizsa, Gaetano (April 1976). Subjective Contours. Scientific American, 4: 48-52 Another example of perceiving objects without the need of the object's reflected light falling on the retina is visual hallucinations. High fever, sensory deprivation, psychoactive drugs, etc. all can cause this experience. ...todd -- Todd Ogasawara, University of Hawaii Dept. of Psychology & U. of Hawaii Computing Center UUCP: {ihnp4,dual,vortex}!islenet! \ \__ uhmanoa!toddo / {backbone}!sdcsvax!noscvax!humu!/ / clyde/ ARPA: OGASAWARAT%HAW.SDSCNET@LLL-MFE.ARPA ** I used to be: ogasawar@nosc.ARPA & ogasawar@noscvax.UUCP
ln63szf@sdcc3.ucsd.EDU (Rick Frey) (07/23/86)
> Visual perception and interpretation is of course based on light striking > the retina. However, reflected light from from an object is not really > the only way to perceive objects. > The best example of this is the filling in process that takes place to > prevent our "perceiving" the blind spot of each eye. At first I thought this sounded ok, but then I found a somewhat significant nit I could pick, so... You're correct that things can be perceived that are not present as stimulation on the retina, but, especially in the example you give, the 'filling in' that takes place is driven by hard-wiring in the neural system that *knows* about this whole in the visual field. Thus, the perceptual information still does not come from the object itself, but from the machinery that knows about the properties of objects. As a criticism in favor of Gibson, this doesn't work. As a statement that there is more to perception than the retinal image, agreed. > Another example is my original dissertation topic: subjective contours. > Artists have long known that you can "suggest" contours and edges by > manipulating the placement of black areas. There are ways to place > lines and black areas to force the visual system to perceive whole > and sometimes complex objects (curved, etc.) Another good example of the perceptual system going beyond the retinal image (or Gibson's "ambient array of light") in order to 'make sense' out of the perceptual information. > Another example of perceiving objects without the need of the object's > reflected light falling on the retina is visual hallucinations. High > fever, sensory deprivation, psychoactive drugs, etc. all can cause this > experience. Many psychologists wouldn't call these 'true perceptions' because their source isn't the perceptual system. It's kind of an odd thought to say that in a dream, you aren't *really* seeing anything, but in many senses (bad pun, I know) you aren't. Rick Frey (...ihnp4!sdcsvax!sdcc3!ln63szf) (ln63szf%sdcc3@sdcsvax.UCSD.EDU or .ARPA)
m128abo@brahms.BERKELEY.EDU (Michael Ellis) (07/24/86)
> Rick Frey >> A Reed >> In this view, the >> natural light sources present in the environment, the reflective >> properties of the surfaces of objects, and the optical characteristics >> of the atmosphere are as much a part of the human perceptual system as >> the eyes and the brain. Thus, the retinal stimulation pattern is not the >> input to perception, but rather an internal stage in the process. The >> input to the perceptual process is the object itself; > >Gibson's major mistake. This simply isn't true. Obviously it has to be >the light that makes it to the organism. If no light reaches the >organism, then there's no perception. Period. Unless the organism >*perceives* the object, it doesn't exist to the perceiver. Perception >starts once there is something to perceive, and that only can begin when >perceptual information about the object makes its way to the perceiver. Major mistake? Simply isn't true? Does anyone understand the relevance of this to Adam's original statement? As far as I can tell, you have simply refused to acknowledge a difference between your word "perceive" and Gibson's. >> the output is >> organism's awareness of the object. The information contained in this >> awareness is the original, and not a re- (or transformed), presentation >> of the object to consciousness. > >Information contained in awareness? This is somewhat Gibsonian in that >he uses words that have no clear definitions, but I don't think even he >would quite say this. What is awareness? What stage of processing are >you referring to? Aside from the actual collection of excited and >inhibited receptors at the retinal level, *all* perception is transfor- >mation. Sorry, no homunculae. (sp??) My, we're being doctinaire! No awareness, no homunculae? All perception is transformation? Are you really sure?? Are you telling us that there is nothing in the real world that corresponds to "awareness"? How quaintly Cartesian! Homunculism is by no means dead. Dennett in "Brainstorms" speaks of mental processes in terms of progressively stupider homunculae. As to awareness itself, are you sure you really wish to overlook the concept? Is all we wish to know about perception simply how a mess of brain cells work? Or is it not at the same time to understand how it is that we become AWARE of our environment? >> According to Gibson, the experimental psychologist's laboratory use of >> two-dimensional representations, tachistoscopic stimuli, illusions, and >> other materials that were not part of the ecological environment in >> which the human perceptual system evolved, amounts to studying the human >> perceptual system with some of its key parts removed. > >In some cases, this is a valid claim of Gibson's, but his whole theory >rests on it and it isn't 100% true. He'd love to have us believe that >the external world is rich in information and that perception is an easy >task of picking out of the multitude of cues available. That's simply >not true. Must the Gibsonians be 100% right lest their entire case come crashing to the ground? Who says so? The anti-Gibsonians? Why? And if Gibson would "love to have us believe the external world is rich in information", whatever do you find hard to believe about that? Do you mean to imply that the world is poor in its information content? As far a I can tell, there IS an enormous wealth of unused information in the natural world. I did not know Gibson's "theory" was either true or false; rather, I thought that it was more unified approach, a redefinition of just what it is our perceptions are, generally in keeping with the wider view of evolution, not of just species, but of interdependent systems ranging from genes to ecologies. If so, there doesn't seem very much to be "wrong" about it, at least none of the criticisms you've offered. >Experimental psychologists aren't blind to this criticism, and far too >many experiments have been done that don't fall under Gibson's >criticisms of artificiality. Perception developed under situations >where the available information was far from over-abundant. Without >this over-abundance of information, Gibson's ideas start falling apart. Totally absurd. Life evolved in the presence of light, which contained vast amounts of environmental information that was almost completely unused until creatures evolved that were complex enough to exploit vision. Or are you denying that light carries information? >Perception developed in a piecemeal fashion such >that there wasn't an overabundance of information at various stages in >the development. So where did this 'perceptual laziness' come into >play? You try finding a small tree frog in a huge tree. The whole idea >of an overabundance of perceptual information might apply to recognizing >people's faces, but it has no basis in the reality of where and how >perception developed. No basis in reality? How different is recognizing people's faces (for beings who need to do so, like other people) from recognizing the kinds of places where frogs hang out (for beings who need to eat frogs)? Now my perceptions did not evolve so that I could locate frogs more readily than many other kinds of things, but if humans had evolved into tree climbers with a diet consisting largely of frogs, I have little doubt that we'd have no trouble locating that frog, even blindfolded. -michael
ln63szf@sdcc3.ucsd.EDU (Rick Frey) (07/25/86)
>> Rick Frey > Michael Ellis > Major mistake? Simply isn't true? Does anyone understand the > relevance of this to Adam's original statement? As far as I can > tell, you have simply refused to acknowledge a difference between > your word "perceive" and Gibson's. Ok, maybe I overstated it a bit. But, when people start playing with words and simply assume that because they feel a certain way they can redefine a word, that's not correct. Perceive is a word with a definition and Gibson's idea of perception doesn't fit the known facts. What more do you want me to say? > >> The information contained in this > >> awareness is the original, and not a re- (or transformed), presentation > >> of the object to consciousness. > >What is awareness? What stage of processing are > >you referring to? Aside from the actual collection of excited and > >inhibited receptors at the retinal level, *all* perception is transfor- > >mation. Sorry, no homunculae. (sp??) > My, we're being doctinaire! No awareness, no homunculae? All > perception is transformation? Are you really sure?? > Are you telling us that there is nothing in the real world that > corresponds to "awareness"? How quaintly Cartesian! Yeah, I feel pretty comfortable saying that all perception is transformation. And be somewhat careful, I never said there was no such thing as awareness, I simply pointed out that it didn't have a clear definition. What do you see in the real world that corresponds to awareness? > Homunculism is by no means dead. Dennett in "Brainstorms" speaks > of mental processes in terms of progressively stupider homunculae. And Don Norman refers to Cognitive demons that make decisions for us, but the idea of the homunculus is that he's sitting in there looking at a television screen that identically corresponds to what we see. This idea of the homunculus is wrong. The little Homunculae you refer to are looking at excited and inhibitted neurons in specific locations. Not quite a tv screen. > As to awareness itself, are you sure you really wish to overlook > the concept? Is all we wish to know about perception simply how a > mess of brain cells work? Or is it not at the same time to understand > how it is that we become AWARE of our environment? I don't want to overlook it at all. But how do we define it? Obviously perception is more than the excitement of neurons, but as far as we can tell, even awareness seems somehow to be linked to a neural state. If you can define awareness, I'd love to know exactly what it is. > >In some cases, this is a valid claim of Gibson's, but his whole theory > >rests on it and it isn't 100% true. He'd love to have us believe that > >the external world is rich in information and that perception is an easy > >task of picking out of the multitude of cues available. That's simply > >not true. > Must the Gibsonians be 100% right lest their entire case come > crashing to the ground? Who says so? The anti-Gibsonians? Why? Nope, he doesn't need to be 100% right. But, since he isn't on a major premise, you have to wonder about his whole theory (that is based on that premise). > And if Gibson would "love to have us believe the external world is > rich in information", whatever do you find hard to believe about > that? Do you mean to imply that the world is poor in its > information content? As far a I can tell, there IS an enormous > wealth of unused information in the natural world. There is an enormous wealth of information, true. But, there is not an enormous wealth of useful information. There's a big difference. > I did not know Gibson's "theory" was either true or false; rather, > I thought that it was more unified approach, a redefinition > of just what it is our perceptions are, But can't general redefinitions be wrong? Obviously he's got some quantity of truth about what he's saying, but in general, his redefinition is off-track. > the wider view of evolution, not of just species, but of > interdependent systems ranging from genes to ecologies. If so, > there doesn't seem very much to be "wrong" about it, at least none > of the criticisms you've offered. But it doesn't make sense in terms of evolution. It works well with identifying faces and familiar objects. That is a far cry from the task of locating predators and prey in a natural environment. > >Perception developed under situations > >where the available information was far from over-abundant. Without > >this over-abundance of information, Gibson's ideas start falling apart. > Totally absurd. Life evolved in the presence of light, which > contained vast amounts of environmental information that was > almost completely unused until creatures evolved that were > complex enough to exploit vision. There's a lot of evolution from light sensitive cells to the eye of a frog, for example. Keep thinking about the task of picking out a cameleon on a tree branch. Do you really have an overabundance of information? Cameleon like characteristics aren't that rare in nature. > Or are you denying that light carries information? Of course not. But it doesn't carry with it how to make sense out of itself. Lots of information, not all of it useful. > >Perception developed in a piecemeal fashion such > >that there wasn't an overabundance of information at various stages in > >the development. So where did this 'perceptual laziness' come into > >play? You try finding a small tree frog in a huge tree. The whole idea > >of an overabundance of perceptual information might apply to recognizing > >people's faces, but it has no basis in the reality of where and how > >perception developed. > How different is recognizing people's faces (for beings who need > to do so, like other people) from recognizing the kinds of places > where frogs hang out (for beings who need to eat frogs)? People's faces aren't typically presented on a background of identical color. People's faces usually don't match the texture of whatever is behind them. People's faces present clear occlusions of other objects such that depth information is pretty clear. Keep thinking about a bumpy green tree frog on a green leaf. Where does the leaf end? A bumpy leaf? Another leaf behind? How do you know? You don't have all day to carefully search each leaf and making a mistake can be fatal. Tree snakes are green, too. > Now my perceptions did not evolve so that I could locate frogs > more readily than many other kinds of things, but if humans had > evolved into tree climbers with a diet consisting largely of > frogs, I have little doubt that we'd have no trouble locating > that frog, even blindfolded. Well tell that to a frog that'll starve to death in a cage full of dead flies because he can't *see* them unless they're moving. An overabundance of information, but little of it actually being useful. Rick Frey (...ihnp4!sdcsvax!sdcc3!ln63szf) (ln63szf%sdcc3@sdcsvax.UCSD.EDU or .ARPA)
dbm@calmasd.CALMA.UUCP (Brian Millar) (07/25/86)
Gibson stressed the point that a theory of perception will focus on the INFORMATION handled by a perceptual system. Thus, the central processor does not "look at" the retina, and does not have to "re-invert" the retinal image. Rather, the retina and central processor form an information handling system which detects the information/structure in the light pattern, and in the physical terrain which generated that light pattern by reflection. To "crack the code" of the visual mechanism requires first knowing what the messages are which it handles. Physiological investigations can benefit from prior perceptual investigations which have determined the basic discriminations of a perceptual system. Gibson also stressed the point that human visual systems may be responsive to highly complex visual patterns which are found frequently in nature. A primary example of this is the texture gradient for a surface in 3-D space. A more complex example is a moving, changing texture pattern, as when an observer moves over a surface in 3-D space. He was impressed by the regularity of these patterns while riding trains as a youngster, watching the rails and ties disappear toward the vanishing point.