Re: IS THIS A COGNITIVE QUESTION ?

Kali wrote:
In <45037620$0$24182$9a6e19ea@xxxxxxxxxxxxxxxxxxxx>, Wolf K El_Lobo_Viejo@xxxxxxxxxxxxxx said: : Kali wrote:
: [...]
: > All very nice. : > : > The OP said (quoted?), "[visual perception is defined as] : > acquisition of knowledge about environmental objects and events : > by extracting information from the light emitted or : > reflected..." You (and Sizemore) object to the use of the term : > "extracting information". : > : > ex·tract (k-strkt)
: > "To derive or obtain (information, for example) from a source"
: : Er, "extract" means to draw out, take out, pull out, distill (as in : chemistry), select (as a sample of a text), to take the root of a : number. It does not mean to derive or obtain. Mind you, you can use it : used metaphorically, as in "extract information". One extracts : information from a prisoner one interrogates, for example; and like : extracting a tooth, it may be a painful process.

Here you are simply contrasting abstract and concrete forms of the word, and then rejecting the intended meaning altogether.

No, I'm contrasting the denotative meanings with a metaphorical meaning, and rejecting the metaphor as misleading and confusing (to put it politely.)

: > "To derive information about the environment from wavelengths of : > light or the reflection of wavelengths of light" : >
: > Tell me how this does not, in generic terms, define visual : > perception? Please explain why this is "really, really funny"? : : Because it is "generic", that is, it's essentially handwaving.

All high level descriptions of complex processes are handwaving, technically. What is your point?

There's handwaving that gestures in the right direction, and there's handwaving that's just - gestures. Which do you think I mean here? (Considering my rather elaborate explications.)

: What's : funny is that it's offered, seriously, in a college level text book. : Either funny or sad.

I have six text books (review copies from different publishers) and all of them describe the process of visual perception quite eloquently. I don't know if the OP was paraphrasing or quoting a high level definition from a source, but it doesn't matter.

Oh yes it does. I don't care how many textbooks you have, or how "eloquently" they describe the process of visual perception. What do they actually say? What's implied by what they say? What kinds of misleading impressions do they give? What do the authors say in trying to make the students aware of misleading interpretations, and what do they do to counteract them? -- A good text helps a student understand the boundaries of ignorance. The quoted (or paraphrased - makes little difference I suspect) definition of visual perception that started this conversation induces an illusion understanding in the student. That's is IMO not merely bad, it's wicked.

: It's also incomplete and misleading, even as handwaving.
: : If information is extracted, then it's "out there." But there is no : reason to suppose that. Light doesn't carry information - it just is. If : you know something of the history of some lightbeam (its source, its : path from A to B, etc), you can use that knowledge to infer something : about the source and/or the medium through which it travelled. Eg, you : can infer some facts about its source and the intervening media if you : pass the light through a prism. But that information is not "carried in : the light." You _construct_ that information by comparison with other : spectra, for example with spectra taken at previous times from known : sources. Without the context of prior data, you can "extract" no : information from the light.
: : In any case, visual perception does not appear to be an extraction : process, but a construction process. That's why I keep directing your : attention to the responses of the rods and cones. We construct our : perceptions from the differences between these responses in space : (location on the retina) and time (series of spike trains from the : retinal neurons). That construction process is very poorly understood. : Hell, even at the level of the whole organism, there are many riddles : about visual perception. Consider selective inattention, for example. We : see what we expect to see, so we miss the stop sign that we do not : expect to be there, and that may have unpleasant consequences.
: : Another example of the poverty of the definition: If perception were : merely an extraction process, eye witnesses would never disagree. They : all received the same information in the light reflected from the : surfaces of the objects they were witnessing colliding with each other, : didn't they?
: : The wave lengths of light do not "carry information". Unless of course : they are modulated to do so, as for example in the system that brings : information from my computer to yours.
: : The definition simply cannot account for the perception of objects, for : example. Or of motion. I mean, what information about the motion of a : batted ball is contained in the wavelengths of light reflected from it? : It reflects exactly the same wavelengths in motion as at rest, after all.
: : The definition does not account for the fact that perception of objects : is not the same as perceiving the colours of light. Nor for the fact : that a collection of different coloured dots will be perceived as an : area of uniform colour if looked at beyond a certain distance. Yet the : "information carried in the wavelengths of light reflected from the : object" is the same regardless of how far away we are from it. So how : come we see coloured dots close up and orangey brown from a distance?
: : Then there is the conceptual difficulty of just what is doing the : extracting. Example: a frog will not attempt to catch a fly-sized object : if it does not move. Yet the information "fly sized object" is there for : it to extract, isn't it? So why does it not try to catch the motionless : fly? Answer: "Because the information "fly sized object" is not in fact : there to be extracted." The frog, like all creatures with visual : systems, constructs its perceptions from the available data. Those data : are not the wavelengths of light, but the responses of its retinal : neurons. The perception of moving flies only is sufficient to keep the : frog fed, so there is no selective pressure for it evolve a more complex : perceptual system.
: : ETC.
:
[...]
: > I generally rely on published research, and experts like : > Kosslyn, Coren, and Enns for information about the visual : > system. I also find the questions more exciting than the : > answers. Your mileage may vary. : : Um, yes. So what's the question about perception that excites you?

"The" question?

Not "the question", but "the question that..." IOW, which of the many questions about perception is the one that excites you?

: I'd never heard of Kosslyn, so i did a quick search. What I got was : secondhand, so it's somewhat unfair to base my impression of his : expertise on it, but it seems to me that he identifies perception with : brain processes. If so, he is in error.

I'm sure he'll be glad to receive your correction.

I doubt it. If the paraphrase and comments I read were a true reflection of his capacity to analyse his won data, he needs more, and more skillful, correction than I am capable of giving him.

: As my analogy with the : accelerating car implies, it's not the brain that perceives, but the : organism. The brain processes implicated in the perceiving can be more : or less well observed, but they do not and cannot constitute perception.
: : I also note that Kosslyn seems to assume "storage of images." It seems : he envisions this storage as a pattern of activation potentials acquired : by a network of neurons, which may be a viable notion.

?Retinotopic maps? - patterns of activation on the surface of retina are found in the LGN as well as the striate cortex (V1). Foveal patterns are larger in V1. There is a similar map found in the termporal lobe for auditory patterns.

Yes, I've known this for so long I can't recall when I first read about it. But these "maps" are in the eyes of the beholders. It's an obvious inference that these "maps" are activation networks, ie, that given the right inputs, they will activate. Functional MRIs (among other data) show that some at least of of these maps are activated when a person imagines or remembers some visual object. This would be true even if the activation networks were so dispersed across the cortex that they wouldn't be recognised by observers. (Actually, some at least of the retinal out output must in fact be so dispersed, since visual cues can activate auditory, tactile, etc, imaging as well as visual.)

To speculate: it's the arrangement of neural events in time and space that constitute the "visual information." IOW, the "form" in "information" is not a metaphor.

: I don't think : enough is known about how neurons form activation networks to be able to : say one way or the other.

There is quite a bit of research published on this, dating back as early as 1965.

I was referring to the biochemistry of strengthening and weakening synapses, activation potentials, and so on. Most of the research you allude to has, until quite recently, shown that such networks form, but how or why. A good deal of it has described some networks in very nice detail. Only recently has there been some insight into how synapses are strengthened and weakened - activation and de-activation of genes seems to be a primary process at this level.

: But whether or no, one thing is clear; the : "imagery" stored in these networks is not image data. It is in fact : indistinguishable from, say, audio data in all respects except one: the : connections of the "storage nets" to other parts of the brain. If the : "storage net" is connected to the visual centres, we remember/perceive : images when it activates. If it is connected to the audio centres, we : remember/perceive sounds. But that's as far as present knowledge will : permit speculation - and IMO only because synaesthesia appears to arise : from crossed or multiplex connections (ie, to both audio and visual : centres.) And even so, it's really handwaving.

Yes, in synasthetes who ?hear? color, as was the case with Kandinsky, hearing words spoken activates area V4, a phenomenon that doesn?t occur in normal subjects. This is just one example; there is also published research on synasthesia involving colors and numbers involving the fusiform gyrus (shapes of numbers), near V4, and the TPO, a higher area of processing that appears to integrate sensory information.

Precisely. Yet the neural spike trains involved do not "carry colour information". They carry information _from or to_ certain areas of the brain. IOW, the structure of the brain, the topology of the neural nets seems to me to be as, if not more, important than the signals.

You call it handwaving. I call it promising research.

The handwaving comes in when we attempt to explain how misdirected signals trigger synaesthetic experience. Such as my claim that the structure of the brain is what matters, not the signals themselves. -- BTW, I am slightly synaesthetic. I get fleeting impressions of colour when I listen to music. These are, as best I can recall, quite consistent, ie, blues and yellows for trumpets, dark reds for tympani, greys for snare drum, orange for cello and bass, reds for violin. But these impression are AFAICT not nearly as vivid as for true synaesthetes. I suspect that mild synaesthesia is quite common, but since the synaesthetic effects are so weak and fleeting, most people pay no attention to them.

.

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