Archive for March, 2016

boxers…for two theories?

Ihtio kindly drew my attention to an interesting paper which sets integrated information theory (IIT) against its own preferred set of ideas – semantic pointer competition (SPC). I’m not quite sure where this ‘one on one’ approach to theoretical discussion comes from. Perhaps the authors see IIT as gaining ground to the extent that any other theory must now take it on directly. The effect is rather of a single bout from some giant knock-out tournament of theories of consciousness (I would totally go for that, incidentally; set it up, somebody!).

We sort of know about IIT by now, but what is SPC? The authors of the paper, Paul Thagard and Terrence C Stewart, suggest that:

consciousness is a neural process resulting from three mechanisms: representation by firing patterns in neural populations, binding of representations into more complex representations called semantic pointers, and competition among semantic pointers to capture the most important aspects of an organism’s current state.

I like the sound of this, and from the start it looks like a contender. My main problem with IIT is that, as was suggested last time, it seems easy enough to imagine that a whole lot of information could be integrated but remain uniluminated by consciousness; it feels as if there needs to be some other functional element; but if we supply that element it looks as if it will end up doing most of the interesting work and relegate the integration process to something secondary or even less important. SPC looks to be foregrounding the kind of process we really need.

The authors provide three basic hypotheses on which SPC rests;

H1. Consciousness is a brain process resulting from neural mechanisms.
H2. The crucial mechanisms for consciousness are: representation by patterns of firing in neural populations, binding of these representations into semantic pointers, and competition among semantic pointers.
H3. Qualitative experiences result from the competition won by semantic pointers that unpack into neural representations of sensory, motor, emotional, and verbal activity.

The particular mention of the brain in H1 is no accident. The authors stress that they are offering a theory of how brains work. Perhaps one day we’ll find aliens or robots who manage some form of consciousness without needing brains, but for now we’re just doing the stuff we know about. “…a theory of consciousness should not be expected to apply to all possible conscious entities.”

Well, actually, I’d sort of like it to – otherwise it raises questions about whether it really is consciousness itself we’re explaining. The real point here, I think, is meant to be a criticism of IIT, namely that it is so entirely substrate-neutral that it happily assigns consciousness to anything that is sufficiently filled with integrated information. Thagard and Stewart want to distance themselves from that, claiming it as a merit of their theory that it only offers consciousness to brains. I sympathise with that to a degree, but if it were me I’d take a slightly different line, resting on the actual functional features they describe rather than simple braininess. The substrate does have to be capable of doing certain things, but there’s no need to assume that only neurons could conceivably do them.

The idea of binding representations into ‘semantic pointers’ is intriguing and seems like the right kind of way to be going; what bothers me most here is how we get the representations in the first place. Not much attention is given to this in the current paper: Thagard and Stewart say neurons that interact with the world and with each other become “tuned” to regularities in the environment. That’s OK, but not really enough. It can’t be that mere interaction is enough, or everything would be a prolific representation of everything around it; but picking out the right “regularities” is a non-trivial task, arguably the real essence of representation.

Competition is the way particular pointers get selected to enter consciousness, according to H2; I’m not exactly sure how that works and I have doubts about whether open competition will do the job. One remarkable thing about consciousness is its coherence and direction, and unregulated competition seems unlikely to produce that, any more than a crowd of people struggling for access to a microphone would produce a fluent monologue. We can imagine that a requirement for coherence is built in, but the mechanism that judges coherence turns out to be rather important and rather difficult to explain.

So does SPC deliver? H3 claims that it gives rise to qualitative experience: the paper splits the issue into two questions: first, why are there all these different experiences, and second, why is there any experience at all? On the first, the answers are fairly good, but not particularly novel or surprising; a diverse range of sensory inputs and patterns of neural firing naturally give rise to a diversity of experience. On the second question, the real Hard Problem, we don’t really get anywhere; it’s suggested that actual experience is an emergent property of the three processes of consciousness. Maybe it is, but that doesn’t really explain it. I can’t seriously criticise Thagard and Stewart because no-one has really done any better with this; but I don’t see that SPC has a particular edge over IIT in this respect either.

Not that their claim to superiority rests on qualia; in fact they bring a range of arguments to suggest that SPC is better at explaining various normal features of consciousness. These vary in strength, in my opinion. First feature up is  how consciousness starts and stops. SPC has a good account, but I think IIT could do a reasonable job, too. The second feature is how consciousness shifts, and this seems a far stronger case; pointers naturally lend themselves better to thus than the gradual shifts you would at first sight expect from a mass of integrated information. Next we have a claim that SPC is better at explaining the different kinds or grades of consciousness that fifteen organisms presumably have. I suppose the natural assumption, given IIT, would be that you either have enough integration for consciousness or you don’t. Finally, it’s claimed that SPC is the winner when it comes to explaining the curious unity/disunity of consciousness. Clearly SPC has some built-in tools for binding, and the authors suggest that competition provides a natural source of fragmentation. They contrast this with Tononi’s concept of quantity of consciousness, an idea they disparage as meaningless in the face of the mental diversity of the organisms in the world.

As I say, I find some of these points stronger than others, but on the whole I think the broad claim that SPC gives a better picture is well founded. To me it seems the advantages of SPC mainly flow from putting representation and pointers at the centre. The dynamic quality this provides, and the spark of intentionality, make it better equipped to explain mental functions than the more austere apparatus of IIT. To me SPC is like a vehicle that needs overhauling and some additional components (some of those not readily available); it doesn’t run just now but you can sort of see how it would. IIT is more like an elegant sculptural form which doesn’t seem to have a place for the wheels.

humoursWorse than wrong? A trenchant piece from Michael Graziano likens many theories of consciousness to the medieval theory of humours; in particular the view that laziness is due to a build up of phlegm. It’s not that the theory is wrong, he says – though it is – it’s that it doesn’t even explain anything.

To be fair I think the theory of the humours was a little more complex than that, and there is at least some kind of hand-waving explanatory connection between the heaviness of phlegm and slowness of response. According to Graziano such theories flatter our intuitions; they offer a vague analogy which feels metaphorically sort of right – but, on examination, no real mechanism. His general point is surely very sound; there are indeed too many theories about conscious experience that describe a reasonably plausible process without ever quite explaining how the process magically gives rise to actual feeling, to the ineffable phenomenology.

As an example, Graziano mentions a theory that neural oscillations are responsible for consciousness; I think he has in mind the view espoused by Francis Crick and others that oscillations at 40 hertz give rise to awareness. This idea was immensely popular at one time and people did talk about “40 hertz” as though it was a magic key. Of course it would have been legitimate to present this as an enigmatic empirical finding, but the claim seemed to be that it was an answer rather than an additional question. So far as I know Graziano is right to say that no-one ever offered a clear view as to why 40 hertz had this exceptional property, rather than 30 or 50, or for that matter why co-ordinated oscillation at any frequency should generate consciousness. It is sort of plausible that harmonising on a given frequency might make parts of the brain work together in some ways, and people sometimes took the view that synchronised firing might, for example, help explain the binding problem – the question of how inputs from different senses arriving at different times give rise to a smooth and flawlessly co-ordinated experience. Still, at best working in harmony might explain some features of experience: it’s hard to see how in itself it could provide any explanation of the origin or essential nature of consciousness. It just isn’t the right kind of thing.

As a second example Graziano boldly denounces theories based on integrated information. Yes, consciousness is certainly going to require the integration of a lot of information, but that seems to be a necessary, not a sufficient condition. Intuitively we sort of imagine a computer getting larger and more complex until, somehow, it wakes up. But why would integrating any amount of information suddenly change its inward nature? Graziano notes that some would say dim sparks of awareness are everywhere, so that linking them gives us progressively brighter arrays. That, however, is no explanation, just an even worse example of phlegm.

So how does Graziano explain consciousness? He concedes that he too has no brilliant resolution of the central mystery. He proposes instead a project which asks, not why we have subjective experience, but why we think we do: why we say we do with such conviction. The answer, he suggests, is in metacognition. (This idea will not be new to readers who are acquainted with Scott Bakker’s Blind Brain Theory.) The mind makes models of the world and models of itself, and it is these inaccurate models and the information we generate from them that makes us see something magic about experience. In the brief account here I’m not really sure Graziano succeeds in making this seem more clear-cut than the theories he denounces. I suppose the parallel existence of reality and a mental model of reality might plausibly give rise to an impression that there is something in our experience over and above simple knowledge of the world; but I’m left a little nervous about whether that isn’t another example of the kind of intuition-flattering the other theories provide.

This kind of metacognitive theory tends naturally to be a sceptical theory; our conviction that we have subjective experience proceeds from an error or a defective model, so the natural conclusion, on grounds of parsimony if no others, is that we are mistaken and there is really nothing special about our brain’s data processing after all.

That may be the natural conclusion, but in other respects it’s hard to accept. It’s easy to believe that we might be mistaken about what we’re experiencing, but can we doubt that we’re having an experience of some kind? We seem to run into quasi-Cartesian difficulties.

Be that as it may Graziano deserves a round of applause for his bold (but not bilious) denunciation of the phlegm.

backwardIn the course of this review of Carlo Rovelli’s Seven Brief Lessons on Physics, Alva Noë asks a fascinating question: does it make any sense to imagine that one might think backward?

In physics we are accustomed to thinking that entropy always increases; things run down, spread out, differences are evened out and available energy always decreases. Are cognitive processes like that, always going in one underlying direction? Are they like a river which flows to the sea, or are they more like a path we can take in either direction?

Well, we can’t talk backwards without careful preparation, and some kinds of conscious thought resemble talking to oneself. In fact, we can’t perform most tasks backwards without rehearsal. Unless one takes the trouble to learn zedabetical order, we cannot easily recite our letters in reverse. So it doesn’t seem we can do that kind of backward thinking, at least. We can, of course, read a written sentence in the reverse word order and I suppose that in that sense we can think the same sentence backwards, or ‘backwards sentence same the think’; but we might well doubt whether that truly reverses the thought.

On the other hand, on another level, there seems to be no inherent direction to a chain of thought. If I think of an egg, it makes me think of breakfast, and breakfast makes me think of getting up; but thinking about getting up might equally have prompted thoughts of breakfast, which in turn might have brought an egg to mind. The association of ideas goes both ways. Logical thought needs a little more care. ‘If p then q’ does not allow us to conclude that if q then p – but we can say that not-q gives us not-p. With due attention to the details there doesn’t seem to be a built-in direction to deduction.

The universal presence of memory in all our thoughts seems a deal-breaker on reversibility, though. We cannot forget things at will; memories constantly accumulate; and we cannot deliberately unthink a thought in such a way as to erase it from recollection. This one-way effect seems to be equally true of certain kinds of thought on another level. We have, let’s say, a problem in mind; all the clues we need are known. At some point they come together to point to the right conclusion – Aha! Unless we find a flaw in our reasoning, the meshing of the clues cannot be unpicked. We can’t ununderstand; the process of comprehension seems as irrevocable as the breaking of an eggshell or the cooking of a omelette.

There’s an odd thing about it though. The breaking of the egg is an example of the wider principle of entropy; the shell is destroyed, and later the protein is denatured by heat. The solving of the problem, by contrast, is constructive; we’re left with more than we had before and our mental contents are better structured, not worse. Learning and understanding seems like a process of growth. Like the growth of a plant it is of course just a local reversal of entropy, which has to be paid for through the use of a lot of irretrievable energy; still, it’s remarkable (as is the growth of a plant, after all).

Hang on, though. Isn’t it the case that we might have been entertaining a dozen different ideas about the possible solution to our problem?  Once we have the answer those other hypotheses are dropped and indeed may even be truly forgotten. More than that, the right answer may let us simplify our ideas, the way Copernicus let us do away with epicycles and all the rest of the Ptolemaic system nobody has to think about any more. Occam tells us to minimise the number of angels we require for our theory, so isn’t the growth of understanding sometimes a synthesis which actually has the character of a reductive simplification? That isn’t usually a reversal as such, but doesn’t it involve in some sense the unthinking of certain thoughts? David Lodge somewhere has a character feel a pang of pity for all the Marxist professors in the universities of no-longer-communist countries who must presumably unspool years of patient theoretical exegesis in order to start understanding the world again.

Well, yes, but I don’t think that is truly an unthinking or reverse cogitation. Is it perhaps more like a plant managing to grow downwards? So no, as Noë implied in the first place, it doesn’t really make sense to imagine we might think backward.