(Note: I've put a lot of words in scare quotes. These are terms that I hesitate to use because they connote things that may be untrue of human experience. I use them only for lack of better words.)
All of us who have done any reading in psychology are well aware of the fact that our brain takes in information as it is presented by the world and then parses it up in meaningful ways. Among the aspects of experience that we agree are produced in this way are: the pitch, timbre, and loudness of sound; the shape, distance, hue, size, brightness and saturation of sight; the sweetness, sourness, bitterness, and spicyness of taste and smell; the temperature, texture, and firmness of touch; and certain bodily senses such as proprioception and our kinesthetic sense. There is very little, if any, dispute that these things aren't determined by separate (some would say distinct, but I won't) parts of our nervous system.
We also recognize that our sensory experience is holistic rather than sequential. If someone tickles our chin and our big toe at the same time, we don't feel it at different times even though it takes the signal much longer to travel all the way up from the big toe. Instead, our brain produces the experience for us of being in both of these states at the same time.
It is my view that mental states are presented to consciousness in the same way as sensory states. Thought, emotion, decision, intention, will, choice, belief, knowledge, concepts, language are all "computed" prior to our experience of them. We do not as experiencers, as conscious beings choose to do things and we don't in the same way know things. Instead, we find ourselves choosing and find ourselves knowing. We (as conscious experiencers) don't directly control these things. We do, however, have veto power. That is, if we don't like the response that our body initially produces we can opt out, and the body will respond with the next subjectively "probable" alternative. (More on this veto power, later.) In some respects, this corresponds to parts of our folk psychology; for example, it gives us some explanation as to why some people seem to think faster than others. It is simply taking a longer time for the one brain to produce the whole experience than the other brain needs.
(This of course has implications for our free will and our morality, but--unlike most neuroscientists who've explored this topic--I will ignore those issues as being not directly important with respect to understanding consciousness. It's up to philosophers to decide if they still want to call this thing free will or that thing morality.)
But doesn't this make consciousness an epiphenomenon? Not entirely, I say. Evolutionary theory gives us plenty of reasons to believe that an epiphenomenon could never truly evolve, especially not one so complex and detailed as our unified experience. Instead, consciousness (experience) must have some function. According to my view, that function is simply to learn about the world. In some sense, it could be said that our brain "learns" things independently of experience, but each "module" of the brain only "learns" its own thing, and that doesn't really tell us much about how the world is. For example, a part of the brain "knows" it is seeing yellow, another feathers, another a chirpy song, but it is only unified experience that can label such a thing a canary.
But how does consciousness learn? And how does the rest of the brain get the benefits of consciousness? Well, I claim, the function of consciousness is to "rewrite" the "program". Surely, like any creature, in order to survive we need to be able to modify our experience, hence the veto power. Maybe you learn from your experience that small animals can feel pain. Maybe you find yourself with the disinclination towards your own pain. A little reason and rational thought may convince one that one ought not to harm these creatures. But, as we all know, suppressing a natural reaction is a hard thing to do and requires a lot of time and concentration. (Such would explain the hangover I have while writing this.) The reason such behavioral modifications take so much time and resources is that the way in which your "program" gets "rewritten" is by having contrary experiences (along with having a certain pro/com attitude towards those experiences). We learn logic, for example, not naturally (as studies of persons who never attended college will clearly show) but through a desire to be more logical and quite a bit of practice. One might also note the importance of external environment to these factors. If one does not have access to appropriate teachers or texts of logic, one will not develop the skill. This is especially true if the person gets to be a significant age before even exploring logic (and I don't just mean formal logic here). It would be very difficult for such a person to ever learn logic, but perhaps not impossible. Another example of the importance of environment may be in our moral education. If as youngsters we aren't exposed to the kinds of behaviors that are virtuous and if we aren't punished when committing vicious acts, we will have a difficult time learning (and perhaps never will learn) how to be a virtuous person. Psychological studies will support this tendency.
This much of my view is well-documented in the literature and is held in some version or other (maybe never in complete correspondence with what I've said) by scientists such as Hans Kornhuber, Benjamin Libet, Michael Gazzaniga, and Max Velmans.
Where I move beyond this view is in saying that this grasp of understanding consciousness gives us a tremendous insight as to what is going on in the case of autistic persons and persons elsewhere on the autistic spectrum. There are currently five types of disorder on the spectrum, and they are often dramatically different. The primary reason that the disorders are said to be on a single spectrum is that there is a broad range of symptoms and they often overlap in unusual or unique ways. What persons with these disorders have in common is problems with social interaction and unusually repetitive behaviors. The actual symptoms of any individual will far exceed this limited correlation and very frequently include such things as sensory difficulties. The sensory problems can be hyper- or hypo-, and you will usually have some of each in the same individual. For example, a person might be extraordinarily adept at hearing tones, but be barely capable of discerning different volumes. These sensory problems are one of the key factors that has led me to accept the above view.
My research on autism has led me to believe the following: The brains of autistic persons are not completely successful at unifying sensory (and other mental) information before presenting it to experience, consciousness. Another possibility is that some information somehow bypasses whatever mechanism does the unifying in the brain and instead goes directly to experience. This view helps to explain these sensory problems. It works something like this: The brain is trying to learn as much as possible about the outside world. If there is some impairment to its most basic functions, we'll end up having a consciousness that is very different from what we do in fact have. Try to imagine seeing every microscopic detail of a thing all at once. Such an experience would be simply overwhelming. Well, we have good evidence to believe that autistic persons are exposed to extreme quantities of information in a similar way. As a natural reaction, the person often suppresses the information and tries to avoid it. This can explain both the hyposensitive properties and the hypersensitive properties of his experience. The negative aspect of his experience may be difficult enough for his consciousness to "rewrite" the "programming" in such a way that it ignores such stimuli. However, no consciousness could survive doing this with every sensory modality, so consciousness will attend to at least one modality, learning very much about it, recognizing patterns, and leading sometimes even to savant-like abilities (such as those of Rain Man). It is my belief that if we extend this basic sensory case to all modes of thought, and consider the consequences of being a consciousness in a state of impairment wherein his mental states are not unified in experience, such that they either are misaligned (one might see one's hand knock on the door before one hears it) or there is no aligning going on at all. I have yet to become aware of a symptom of an autistic disorder that cannot be sufficiently explained on this model.
The variety of age of onset of symptoms (sometimes as late as four years) in the autistic disorders gives us some reason to think that the general picture described above is simplistic, but I believe that if we coordinate our studies of autism and consciousness, we'll learn very much about both.
(C)2005, Kevin Schutte