Thursday, October 15, 2020

Synchronization and the unity of consciousness

The problem of the unity of consciousness for materialists is what makes activity in different areas of the physical mind come together into a single phenomenally unified state rather than multiple disconnected phenomenal states. If my auditory center active in the perception of a middle C and my visual center is active in the perception of red, what makes it be the case that there is a single entity that both hears a middle C and sees red?

We can imagine a solution to this problem in a computer. Let’s say that one part of the computer has and representation of red in one part (of the right sort for consciousness) and a representation of middle C in another part. We could unify the two by means of a periodic synchronizing clock signal sent to all the parts of the computer. And we could then say that what it is for the computer to perceive red and middle C at the same time is for an electrical signal originating in the same tick of the clock to reach a part that is representing red (in the way needed for consciousness) and to reach a part that is representing middle C.

On this view, there is no separate consciousness of red (say), because the conscious state is constituted not just by the representation of red (say) in the computer’s “visual system”, but by everything that is reached by the signals emanating from the clock tick. And that includes the representation of middle C in the “auditory system”.

The unification of consciousness, then, would be the product of the synchronization system, which of course could be more complex than just a clock signal.

This line of thought shows that in principle the problem of the unity of consciousness is soluble for materialists if the problem of consciousness is (which I doubt). This will, of course, only be a Pyrrhic victory if it turns out that no similar pervasive synchronization system is found in the brain. The neuroscience literature talks of synchronization in the brain. Whether that synchronization is sufficient for solving the unity problem may be an empirical question.

The above line of thought also strongly suggests that if materialism is true, then our internal phenomenal timeline is not the same as objective physical time, but rather is constructed out of the synchronization processes. It need not be the case for this that the representation of red and the representation of middle C happen at the same physical time. A part further from the clock will receive the synchronizing signal later than a part closer to the clock, and so the synchronization process may make two events that are not simultaneous in physical time be simultaneous in computer time. I suspect that a similar divide between mental time and physical time is true even if dualism is (as I think) true, but for other reasons.


Michael Gonzalez said...


Does "materialist" forbid thinking that seeing red and hearing Middle C have nothing to do with representation, do not occur in the brain, and are not analogous at all to a computer processing different kinds of signals? What if a person thinks that seeing red and hearing Middle C are first-order powers of animate creatures with functioning eyes and ears, with no need of representations at all? Of course they need to have well-functioning brains to achieve this, just as they need functioning brains to walk and talk; but there is no question that it is the living animal that walks and talks (not its brain), and no real question of "what makes it be the case that there is a single entity that walks and talks".... Such a person still only thinks the physical living creature exists, actively embedded in its environment and skillfully engaging with it. But they don't think that seeing is a matter of processing anything in the "visual centers" of the brain. Are they still "materialists"?

I should mention in passing that there are various experiments which cast doubt on the idea that there are "visual centers of the brain" in any very strict sense (Dr. Mriganka Sur at MIT, for example, with his ferrets). But, the deeper conceptual issue cannot be addressed scientifically, since it concerns the meaning of terms like "see" and "hear" and whether these can intelligibly be described in terms of representation.... After all, in normal representations (like paintings), there is a non-representational medium in virtue of which it can be perceived to be the representation it is (i.e. the paint and its properties, the canvas and its texture, etc.). No such thing exists for merely seeing some red object in the world.

IanS said...


I doubt that consciousness is as unified as it seems. We may seem to experience different things simultaneously, but do we really?

Recall this old joke. Q: How do you make your sore toe hurt less? A: Bang your head against a brick wall. If asked, you would say that your toe hurts a bit and your head hurts a lot. But it’s not so easy to experience both pains at once.

I’m listening to music. I become aware of a person at the door. Can I say at which note I first noticed the person? Not in my experience. I can recall a ‘before’ state (listening to music) and an ‘after’ state (seeing the person at the door). But precisely when and how one state changed to the other is a blank, at least in my experience.

Examples like these could be multiplied. The (tentative) moral I draw is that consciousness is less unified than it seems, that there is no single internal timeline, and that the timeline we recall is constructed after the event.

Dominik Kowalski said...

None of that is an example against the unity of consciousness

IanS said...

Well yes, neither example is conclusive, but both are suggestive. Maybe I really did have a unified experience of noticing the unexpected visitor at the door and hearing a particular note, but did not commit the note to memory (or maybe I later forgot it). It might have happened that way. But it might also be that I never had the unified experience to start with. How could I know?

I doubt that there could be a conclusive example against unity of consciousness – the ‘refrigerator light’ problem would prevent it. (You always see the refrigerator light on, because opening the door turns it on.) If you consciously attend to anything, well, that’s what you are conscious of.

Alexander R Pruss said...


But all that the arguments against materialism from the unity of consciousness need is one instance of unity of consciousness between awarenesses realized in different brain areas. The existence of many examples of lack of unity of consciousness does no harm to these arguments.

William said...

It depends.

Modern instruments can operate far faster than human senses can perceive. So we need to define unity of consciousness to be unity over an interval that the mind can perceive, or we can always find a shorter duration, over which there is no unity.

Some measures of brain activity, such as cortical EEG, measure using units and intervals shorter in time than the briefest expressible human awareness. Others, such as fMRI, measure intervals that are quite a bit longer than a typical single thought.

So if we seek evidence for unity of consciousness we find such unity is easy to read from fMRI, but not so clearly present with cortical EEG.

So, synchrony in experience has to be synchrony during an interval, and that interval's needed length in time for humans is not clear. It's certainly more than a millisecond and probably less than a quarter second.

IanS said...


One could doubt (I would not put it more strongly than that) that consciousness is ever unified. Granted, it usually seems so. But how could we be sure? The ‘refrigerator light’ problem cuts both ways.

I’m not seeing that the post is an argument against materialism. As you say, it is an empirical matter whether the required synchronizing mechanism exists. Also, the picture of ‘awareness realized in different brain areas’ may be too simple. Usually, we are not conscious of a visual field and a soundscape. Rather, we see objects, some of which we take as producing sounds. We see, for example, a red patch as a car that is making the ‘brmm brmm’ sound we hear. This must be the result of high-level behind-the-scenes processing that interprets the red patch as a car and ties the sound to it, before they are even reach consciousness.

I’m not defending a materialist account of mind – how nerve impulses could produce (or amount to) experiences is a hard problem. But I don’t see that the post advances the case against it.

Alexander R Pruss said...


This post was meant to save the materialist from an objection, not to provide evidence against materialism. But see below...


This isn't completely clear to me. Imagine that for me seeing red started a picosecond before noon and a picosecond after noon I started feeling pain, while for you the reverse happened. Two picoseconds is likely well below the timing of any relevant brain synchrony processes, and far below anything discernible to us. Nonetheless, there is a fact of the matter that I had red before pain and you had pain before red. And if we were annihilated exactly at noon, then I would have had red without pain and you would have had pain without red.

Now you might say that it makes no sense to say that my seeing red started at some time t with such precision that t is determined to the picosecond. But surely at any given time, either I am seeing red or I am not, and it's never the case that I am both seeing red and not seeing red. So if I didn't see red at 11 am, and I did see red at 1 pm, there must be a moment of time such that at that time I see red but a picosecond earlier I did not. That's just classical logic, plus the assumption that time between 11 and 1 divides into picoseconds.

The only way out I can see for a materialist (and maybe even a dualist) is to suppose that phenomenal time is a different kind of time sequence from external time.

William said...

You are right that we could theoretically measure the edges of a perception of unity to the picosecond, but I also think that a difference of 2 picoseconds in an experience would not be anything a subject could reliably notice or report as a phenomenal difference in the feelings.

So though there's no doubt there would be a real difference in the time order in your example of +/- 2 picoseconds, I do not think the subjects themselves would be able to tell without guessing, or checking the recording equipment themselves.

I think the issue is not the phenomenal sequence being different in order alone, though I expect there would occasionally be such a difference (noticing a light before a smell for example, even though they hit eye and nose in a different order, say nose then eye).

Rather, there is a kind of granularity in phenomenal time, due to human limits causing required intervals for a change to happen in what we sense, so that some differences in objective time and time sequence can be distinguished with instruments, but the phenomena cannot in experience be distinguished in time by the subjective consciousness.