Tuesday, January 31, 2012

Psychophysics and Consciousness

I reread this paper by David Chalmers yesterday morning for the first time in several years. I had been reminded of it because of this commentary by Kaspar Meyer in Science last week. The commentary was mildly interesting, and pointed out some of the current neuroscience perspectives as to just what consciousness is: e.g. is it the sensory experience with a background of knowledge and cognitive processes ("bottom up"), or is it a sort of best-estimate of what reality is given current and recent circumstances, using sensory input as a sort of reality check ("top down")? He finishes off in what seemed to me to be pretty fuzzy territory, but it was at least evocative of interesting ideas.

I'm vaguely familiar with some of this stuff, but I've never gotten too deep into because it doesn't satisfy me the way the philosophers do. The neuroscientists are looking for the "neural correlates of consciousness", which I guess is all that one really can look for. What this science reveals is the structure of consciousness, i.e. what is and is not included, what are the boundaries and how are they determined by the nature of the brain, and as indicated above, what exactly is the seeming 'core', or experiential reference point, of conscious experience, in neurobiological terms.

It is good stuff, but it always seems to me that the proposed theories far outstrip the basic science that is supposed to underpin them (e.g., in the commentary, Meyer cites experiments that demonstrate internally generated excitation of sensory cortex, and more generally recurrent activation, as evidence for the interesting idea that perceptual experience "would result from signals that descend through the sensory systems, just as behavior results from signals that descend along the motor pathways"). I don't know, that seems a bit of cart before horse, but like I said, I've only ever really skimmed the surface of this research. Meyer, Damasio, Dehaene, these guys are all basically frontal cortex cognitive neuroscientists, not perception scientists, and I've never really had cause to sink into that part of the science.

Now, the Chalmers paper. That's what I was going to go on about, not the Meyer commentary...

Anyways, in that paper Chalmers isn't really describing new ideas or new ways of thinking about consciousness (there is a subsection on some sort of "Kripkean" analysis of some philosophical point which I think actually subtracted from my comprehension of other parts of the paper, but it doesn't seem crucial). What he does is lay out a taxonomy of theories of consciousness - and the consciousness he's talking about isn't the "easy" kind, as he calls it, i.e. the NCC business that Dehaene is always going on about, but the "hard" kind, i.e. the fact-of-phenomenal-experience. I was thinking about that taxonomy yesterday evening, and wondering how psychophysics as a science fits into it, whether or not it biases one towards one or another way of thinking about phenomenal consciousness and just what it could be, or where it might come from.

As far as I know, the only visual psychophysicist who has written extensively (in English) on the philosophy of perception is Stanley Klein. I'm sure there are others, probably some I have heard of, but for now I'm guessing that if they exist they are writing in German or Italian. Klein is a proponent of the idea that phenomenal consciousness has something to do with quantum physics. Chalmers categorizes this sort of idea as dualist, since it supposes that consciousness is a quantum epiphenomenon of the activity of the physical brain. In other words, there is the brain and its physical structure, then there is a corresponding, consequent pattern or structure of quantum effects, and it is those effects that correspond to subjective, phenomenal consciousness.

I never liked this idea, at all. It usually relies on the Copenhagen interpretation of quantum mechanics to make the connection between observation and collapse of a wave function, which is the same thing that leads to that horrible Schrodinger's cat story. Not that I'm qualified to really have an opinion on this stuff, but that interpretation - that multiple possibilities exist simultaneously until selected by "observation" - is obviously nonsense, and just exists to show that something is not properly understood about the whole situation.

Okay, so I've shown myself to be a quantum mechanics ignoramus. Anyways, the QM-as-consciousness stuff is a type of dualism according to Chalmers, and I think it's quasi-mysticism, but does it have any currency among psychophysicists? I doubt it. I think Klein carries it because he was a student of Feynman who went into psychology, and he couldn't help but make the connection. He's an order of magnitude smarter than I am, maybe, but I think he's wrong.

As scientists, we might expect that psychophysicists should be materialists according to Chalmers' taxonomy. When I first got interested in perception and psychophysics was back when I was reading every bit of Daniel Dennett that I could find, and he is really the popular standard bearer of materialist theories of phenomenology (or was back in the 90's; this was the same time that I read Blackmore's "Meme Machine", and became completely obsessed with those ideas for a good couple of years). The idea here is that consciousness, in a way, doesn't actually exist; all that exists is the interconnected and multilayered and recurrent set of mechanisms for relating sensation to action over many timescales; in other words, "the mind is what the brain does". The fact that we have the impression of "looking out", or of being somehow spatially immersed in our thoughts and percepts, is a sort of necessary fiction that helps all those mechanisms to bind together and work correctly.

I'm not sure, but I think that J.J. Gibson might have been the closest thing (in the previous academic age) to a philosophical materialist in vision science. I suppose that most vision scientists adhere to a much more nuanced form of materialism, since Gibsonian materialism, or direct realism, is not really in good repute these days. I really like the idea in general, and consider it a good null hypothesis for study of perception - i.e. the perceptual world is the physical world that we tend naively to identify it with, and not a "representation" of the physical, and a given brain is a locus of limitations on what is known or remembered or simply accessible about this world.

Cognitive and perceptual neuroscience in general usually makes claims about consciousness that are consistent with the materialist position, i.e. that consciousness is the set of processes and functions of the brain. Chalmers says this (about neuroscience) explicitly. I always feel, though, (and I think that somewhere I've seen a talk by Dehaene where he says as much) that this is a terminological confusion, and that the neuroscientists must generally know, but forget sometimes, that the hard problem of consciousness, of phenomenology, is not addressed by their studies. Again, you know, I just have superficial acquaintance with this research, and maybe it's a common complaint amongst the Dehaenists that outsiders are always complaining that they (Dehaenists) are claiming that they're studying something that they aren't, when of course, duh, the Dehaenists know the difference. Oh well.

Finally, we wrap things up by mentioning what Chalmers calls monism, which is ultimately pan-psychism or pan-subjectivism. Reality has its relational, "objective" properties, and also its intrinsic, "subjective" properties. Phenomenal consciousness is simply the intrinsic nature of a functioning brain. This is an old idea, thousands of years old maybe, but it's not scientific. It's anti-scientific, even, since it's a claim that science, being the study of the objective nature of reality, can by definition not touch phenomenal consciousness. I think this is probably the truth of things, too, and it's kind of irritating. Anyways, is this a common feeling amongst psychophysicists, that the ultimate object of their study (whether or not they admit it; behaviorist materialism is a necessary stance for formulating good scientific theories of perception) is by definition un-attainable? That might be the answer right there; there's an operational stance (materialism), and a functional stance (monism), and only one of them - the wrong one - will ever get you anywhere.

I guess I'm going to have to start questioning psychophysicists. It will require a certain amount of drunkenness, I'm sure...

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