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]>
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
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
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
the moving texture of your skin as you move your finger up and down
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
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
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
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.
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