Cohen & Dennett’s Perfect Experiment

I was re-reading Dennett and Cohen’s recent paper in Trends in Cognitive Science, “Consciousness Cannot be Separated from Function” and I am now puzzled by their view (before I go on, I would like to note that this issue of TICS also has Joe LeDoux’s paper where he mentions the Qualia Fest, and Lau & Rosenthal’s paper…all in all a great issue!).

Cohen and Dennett want to argue against phenomenological overflow, which is a debate I am currently in the middle of myself, by showing that it is essentially an unscientific view. To do this they introduce what they call the ‘perfect experiment’. They imagine that the area of the brain that is responsible for processing color is somehow allowed to function but is isolated in such a way that it cannot be accessed. The subject in this experiment is shown a blue cup, say, and will deny that they see the color even though the isolated brain area is doing what it normally does. They say,

In spite of this frank denial by subjects, theories that posit dissociation between consciousness and function would necessarily assume that participants of the ‘perfect experiment’ are conscious of the apple’s color but simply cannot access that experience. After all, the conditions these theories stipulate for phenomenal consciousness of color are all met, so this experiment does not disprove the existence of isolated consciousness; it merely provides another particularly crisp example of consciousness with- out access.

However, there is a crucial problem with this logic. If this ‘perfect experiment’ could not definitively disprove [overflow theories] theories, then what could? The subject man- ifests all the functional criteria for not being conscious of color so what would ground the claim that the subject nevertheless enjoys a special kind of consciousness: phenomenal consciousness without access consciousness

I think it is interesting to note that this kind of argument against overflow has been around for a long time. Here is a passage from Huxley’s On the Hypothesis that Animals are Automata, and Its History (from 1874),

If the spinal cord is divided in the middle of the back, for example, the skin of the feet may be cut, or pinched, or burned, or wetted with vitrol, without any sensation of touch, or of pain, arising in consciousness. So far as the man is concerned, therefore, the part of the central nervous system which lies beyond the injury is cut off from consciousness. It must be admitted, that, if any one think fit to maintain that the spinal cord below the injury is conscious, but that it is cut off from any means of making its consciousness known to the other consciousness in the brain, there is no means of driving him from his position by logic. But assuredly there is no way of proving it, and in the matter of consciousness, if anything, we may hold the rule, “De non apparentibus et de non existentibus eadem est ratio.”

The latin phrase there means something like “things that can’t be detected don’t exist.” As Huxley himself points out in the matter of consciousness, if anything, this seems correct. What sense can we make of a phenomenally conscious state that one is in no way aware of?

But it seems to me that these kinds of arguments need to deal with the mesh argument that Block defends. If the mesh argument works (I don’t think it does, at least not in favor of overflow), then we have an answer to the perfect experiment. We say that there is unaccessed consciousness in the isolated brain region because that is the (allegedly) the best over-all interpretation of the data coming in from neuroscience and psychology. Just to repeat, I DO NOT think that there is overflow but I do think that the above kinds of arguments need to deal with the mesh argument directly so I don’t find Cohen and Dnnett’s paper to advance the debate.

7 thoughts on “Cohen & Dennett’s Perfect Experiment

  1. I am with you on this one, Richard.

    It seems to me that another way of putting the same point is to say that Dennett & Cohen are not entitled to merely stipulate that “the subject manifests all functional criteria for not being conscious”. This is because according to an advocate of mesh + overflow, some of the functional criteria will include functional properties of brain-areas that are inaccessible in the ‘perfect experiment’. If inference to the best overall explanation dictates that these areas are sufficient for consciousness, then we should conclude that the subject in the ‘PE’ is conscious of color despite the lack of the overt, easily observable behaviors (esp. verbal reports) that we would ordinarily expect in cases of color-consciousness. Since there’s dispute about the relevant functional criteria, some substantive arguments need to be given here (presumably at the level of overall IBE?).

    Does that seem like a fair re-statement? I must admit I haven’t been keeping up with the cutting edge of this debate, but that’s my gut reaction.

    Also thanks for drawing attention to the Huxley quotation. I’ve never keyed in on that particular bit before, and I think my students will get a kick out of it when we cover Huxley next week!

  2. Brian, that seems not quite right to me. D&C make it pretty clear early in the article that “function” is shorthand for “cognitive function” or, even better, “higher-level cognitive function”. So, the subject in the perfect experiment does indeed manifest all the functional criteria for non-consciousness, even by the lights of Block and Lamme. And as for what the overall IBE of consciousness is, it’s not like Dennett hasn’t had anything to say about that during his career.

  3. I agree with Pete that Brain’s way of putting it is not the same as my way of putting it. I was granting that the subject would act in all ways as though they had no conscious experience, but it might still be a consequence of our best theories that they in fact did have conscious experience. The mesh argument basically says that if you accept that there is more to phenomenal consciousness than is accessed at any given time you can see how results from neuroscience and psychology line up nicely. If that works then it shows that in the PE there is conscious experience. And consequently the charge of overflow being non-scientific is gone. So I was mostly complaining that they don’t engage with this move at all.

  4. “What sense can we make of a phenomenally conscious state that one is in no way aware of?”

    Here you appear to define “aware” in the narrow sense that the person can demonstrate that awareness, since that is the distinction between access consciousness and phenomenal consciousness. But if you take “aware” to have a larger meaning it can be made sensible.

    For example, consider someone who is apparently in a coma, yet is aware. Someone such as Sarah Scantlin during her 20 year coma.

    Suppose that an anesthetic worked by temporarily paralyzing the patient while inhibiting the formation of long-term memory. So that although a brain scan might show the hallmarks of pain, the patient would be forever unable to report any pain. Wouldn’t this pain satisfy the definitions as being a part of phenomenal consciousness but not access consciousness? Would such an anesthetic be ethical to use?

    However, I don’t think the problem dualism (or idealism) addresses is one where the internal experience is merely inhibited, but rather one in which it cannot be conceptualized. We experience greenness, but we have no conception of the qualia that are the essence of the experience of greenness. Objectively, we can correlate many things to the experience, such as a certain frequency of light or the excitation of certain neurons, we might even be able to construct a device that says “green” when ever green light falls on it; but these things don’t equal the experience of greenness.

    The brain activity associated with the experience of greenness might be taken as an outward and visible sign of an inward and spiritual grace. Does complete correlation always equate to complete identity?

    Is the concept of reality identical to the reality itself? If all experience is conceptualized, then how can there be a difference? Clearly there is some experience that is not conceptualized. That makes the difference between the real and the concept of the real. That difference is solely in the qualia–the unconceptualizable experience.

    The idea that there is no distinction between an experience and the concept of that experience may be very attractive for a philosopher.

  5. Dennett has performed a sleight of hand that appears to have been ignored by philosophers. He has shunted the “hard problem of consciousness” into the physical world beyond the body and nobody seems to have noticed. See Dennettian Dualism. Of course, once you have the tacit acceptance of this trick it is easy to argue mechanistically about the functions of the brain.

  6. Is it not also pretty contentious to appeal to such a narrow view of science? As a criticism the strength of the argument seems to appeal from the verification principle

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