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Date:         Fri, 21 Nov 1997 22:01:36 +0000
Reply-To:     "PSYCHE Discussion Forum (Biological/Psychological emphasis)"
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Sender:       "PSYCHE Discussion Forum (Biological/Psychological emphasis)"
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From:         Aaron Sloman <[log in to unmask]>
Subject:      Baars on Binocular Rivalry (was Re: Illusions)

"<Bernard Baars>" <[log in to unmask]> Dear Bernie, Thanks for your rapid response to my comment. Apologies taking so long to reply, owing to umpteen other parallel tasks. > Aaron Sloman nails me on something I did not say. He writes, " Quite a lot > of people seem to think that the ONLY possibilities are complete coherent > fusion or binocular rivalry. E.g. Baars claims this unequivocally on page 89 > of "In the Theater of Consciousness" (OUP 1996)" Well, perhaps I mis-interpreted what you wrote. ...But binocular fusion breaks down if there are significant differences between the input to the two eyes. .... if one image is slightly offset from the other, binocular rivalry results, and to obtain coherence the visual system will suppress one image in favour of another. I thought that was pretty unequivocal. And to me it implied that if you are getting two different views one will be suppressed, which is not what happens if you look past a finger pointing upwards and see two fingers both of which are transparent, which is what happens to the people I've asked. (It's also a common textbook example, I think.) Later on the same page (Baars p.89): ... Any significant disparity between the two eyes or ears causes one of the two flows to be suppressed. Conscious perception is always coherent, even if the nervous system needs to cancel (sic!!) some input in favor of another. ... In general, it seems to be impossible for human beings to hold two different interpretations of the same thing in consciousness at the same time. In many cases we can prove that two representations exist fleetingly in the brain but only one can be conscious at a time. And so it goes on. Now to me that reads exactly like the claim I criticised, and which I've also heard from others in the field, and which I think is clearly false for the reasons I gave. But maybe you intended it to say something I've not understood. In your response to me you write: > My claim is that consciousness reflects an internal consistency constraint. > The observations Aaron cites are not internally inconsistent, and do not > contradict that hypothesis. Consider the sorts of superimposed images I described, e.g. resulting in your simultaneously seeing BOTH the moving texture of your skin as you move your finger up and down AND the static texture of the wall beyond the skin as a result of two DIFFERENT retinal images both contributing simultaneously to your current experience. If you claim that that is not a case of internal inconsistency then I have no idea what you mean by "internal inconsistency". It seems to me to be exactly a counter example to what you describe by saying ...if one image is slightly offset from the other, binocular rivalry results... Perhaps you've changed your views slightly since writing those words, as suggested by your comment on my message: > The visual system seems to interpret those > binocular effects as looking through a diaphanous object in one eye and > seeing a solid one in the other. Not in my case: it actually looks as if I am seeing the SAME (inconsistent) thing in BOTH eyes! Doesn't it to you? > ...It looks actually like a really clever and > creative solution to the problem of seeing two different objects, one in each > eye, and giving a consistent interpretation. My suspicion is that with your current view as expressed here, nothing is ruled out: the visual system can in some contexts find a way to accommodate ANY two retinal images. The new theory seems to me to be far more interesting, as well as being true (with qualifications to allow for the cases where rivalry really does occur). It's more interesting because it helps to draw attention to the real creativity of interpretative processes involved in perception, undermining the common view (among scientists) of perception as a (much more boring) process of directly extracting information about the environment through a succession of stages of image analysis. Whether it fits in with the global workspace and searchlight and theatre metaphors is another question. In my experience, searchlights and theatres have the wrong properties to be capable of explaining the phenomena. "Global workspace" seems to be closer to an idea which is frequently reinvented (as you acknowledge) but as yet far too murky. We shall almost certainly have to find an entirely new non-metaphorical way to think about these things, involving the concept of an information state in which various kinds of information about spatial and temporal and functional and causal relationships are integrated in some kind of mechanism, not yet understood at all, which makes that information readily available for a wide variety of tasks. How? What these examples of superposition show is that various sorts of simple-minded ideas about constraints on the kinds of information that can be simultaneously held in this mechanism (e.g. simple notions of "coherence", "consistency", etc.) are wrong. What the facts about rivaly show is that sometimes such constraints do operate. Nothing I've heard about in neuroscience, AI, computer aided design, seems to be adequate to the task of implementing these information states. But that's another story. (I've spelled out, rather crudely, some of the requirements in a paper in the Journal of Experimental and Theoretical AI ,1989, vol 1, no 4. But it's very crude. I'm still trying to expand the ideas in terms of what is to perceive possibilities inherent in a structure.) > I don't know of a persuasive counterexample to the consistency hypothesis. > It's just an empirical question --- does anybody know of one? Maybe it's not an empirical question if the phenomena described above are not counterexamples. Aaron


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