I was struck by the following imaginary dialogue in a recent article by Michael Cohen and Daniel Dennett. In the dialogue, P is a patient and F&L are Fahrenfort and Lamme, the targets of C&D's critique.
F&L: ‘You are conscious of the redness of the apple.’I think we are meant to find F&L's insistence preposterous, or at least misguided.
P: ‘I am? I don’t see any color. It just looks grey. Why do you think I’m consciously experiencing red?’
F&L: ‘Because we can detect recurrent processing in color areas in your visual cortex.’
P: ‘But I really don’t see any color. I see the apple, but nothing colored. Yet you still insist that I am conscious of the color red?’
F&L: ‘Yes, because local recurrency correlates with conscious awareness.’
P: ‘Doesn’t it mean something that I am telling you I’m not experiencing red at all? Doesn’t that suggest local recurrency itself isn’t sufficient for conscious awareness?’
Is it preposterous or misguided? I feel the attraction of saying so. But imagine this parallel case, in which the patient's report is of a visually seen object and the scientists are speaking to the patient from another room in the building:
Scientists: ‘You are looking directly at an apple that is on the table two feet in front of you.’[Update, Mar. 16: Just to be clear: The dispute I am imagining is not about P's mental life. It's about the fact of whether there is actually an apple on the table.]
Participant: ‘I am? I don’t see an apple. It just looks like an empty table. Why do you think I’m looking at an apple?’
S: ‘Because we put the apple there, and we are monitoring it with a suite of video cameras and other devices [fill in further convincing details].’
P: ‘But I really don’t see an apple. I see the table, but no apple on it. Yet you still insist that there's an apple there?’
S: ‘Yes, because [repeat suite of persuasive empirical evidence].’
P: ‘Doesn’t it mean something that I am telling you I’m not seeing the apple? Doesn’t that suggest that your video cameras, etc., are broken?’
Here's my thought: This is a fairly bizarre situation. One wonders if the scientists' cameras are broken after all. But whether to believe the scientists or the participant is going to depend on further details. How trustworthy is the scientists' equipment? Is there some plausible reason to think the participant might really be mistaken? For example, what if the participant had been given a post-hypnotic suggestion? What if the participant were viewing the apple monocularly and the apple were being manipulated so as to remain always in the participant's blind spot? Then we might have excellent reason to believe the scientists over the participant.
I would suggest that the introspective case is epistemically similar. It doesn't hands-down favor the patient. It depends on the details. It depends on such things as the trustworthiness of the external measure of consciousness and whether a reasonable explanation of the patient's error is available. We should not, contra Cohen's and Dennett's apparent intention, conclude from this thought experiment that self-reports of experience are in any strong sense "incorrigible".
(Dennett and I have already gone around a few times on this issue: here and here and here.)
Update, March 13:
Cohen and Dennett have given me permission to post the following reply on their behalf:
Thanks to everyone for the comments! Here are just a few points of clarification of our view.
For us, the subject's words are not the ultimate criterion or touchstone of consciousness. Not at all! Change blindness and inattentional blindness and many other phenomena demonstrate how people often overestimate their knowledge of their own experiences. But if we want to understand everyday subjective experience—and that is what people have in mind generally when they speak of consciousness—we have to start with the understanding that in general people have access to their own experience! But theorists like Block, Lamme, and colleagues want to go a step beyond that. They want to say that there are conscious experiences that you can't even access yourself. In other words, there are experiences that you can't talk about, you can't report, you can't remember, you can't make decisions about, you can't plan to act in one way or another because of, and even if you're directly probed, you will still not realize you're having it. (This is what Block and Lamme mean when they insist that there can be phenomenal consciousness without access consciousness. (See Lamme, 2003 TICS where he talks about conscious states you can't access or realize you're having).
We do not at all deny that there are instances in which a scientist can make observations about a subject's neural state that the subject can't report. There are too many instances in the scientific literature to list here. For example, it's easy with current technology to measure fluctuations in primary visual cortex (V1) using fMRI to which the subject has no access. Not only can he not report the change in his V1, he can't even recognize something on the screen is changing that is causing those neural changes. The idea that subjective report is the only tool we have for consciousness studies is not at all our view. Our view is that there are two quite well established categories: conscious experiences to which subjects have access, and unconscious processes to which they do not have access. If Block and Lamme want to propose a new category of phenomenal consciousness with no access, they must motivate it. How are they proposing to distinguish it from unconscious activity? In virtue of what properties are the phenomena at issue rightly called conscious? Freud proposed a similar distinction, between totally unconscious and “preconscious” activities, and more recently Dehaene et al (TICS 2006) have updated that proposal with a carefully defended taxonomy of sublimininal, preconscious and conscious activity. Are Block and Lamme proposing to simply rename Dehaene et al’s ‘preconscious’ category as phenomenal consciousness? If so, what don’t they like about the term ‘preconscious’? If not, if they want their taxonomy to compete with this taxonomy, they need to tell us what special features mark the phenomenally conscious but unaccessed activities from Dehaene et al’s preconscious activities.
[For a few of my (ES's) thoughts in reaction, see the comments section, March 13.]