Surely not?    

Is the brain 'massively parallel'? Is the brain a computer? Is the self an illusion? Some ideas have an appeal that gets them widely adopted in spite of their inherent unlikeliness. In the cases below we have a go at some widely-accepted ideas which we think deserve re-examination. It must be pointed out that we are in two or more minds about some of these. We may at some stage, for example, see an entry here which denounces the widely-held view that the brain isn't a computer...


Massively Parallel home

Blandula You frequently see brain processes described as 'massively parallel'. The analogy being suggested is with parallel processing in computers, where a process is divided up and different parts of it are carried out simultaneously by different processors, thereby finishing the job more quickly.

Now the first and best reason why the brain isn't a parallel processor, of course, is because it isn't a computer at all.  But even if it were, there would be no good reason to think the brain is a parallel, rather than a serial processor. Massively parallel processing specifically is a particular, sophisticated form of parallel processing which allows hundreds of processors to work efficiently on the same overall job, such as searching a large database. Each processor typically has its own memory and operating system; where the activities of the different processors overlap, the relationship is carefully managed so that they do not have to remain in step, and this requires careful prior programming. This does not seem to me even remotely like the way the brain is organised, so far as we understand it. There do not seem to be any good candidates within the brain for the role of processor (neurons are surely too simple)and the discrete, managed approach of parallel processing contrasts starkly with the prolific interconnectedness of the brain.

Parallel processing isn't such a big deal, in any case. Turing himself established that all computers are essentially the same: fundamentally they differ only in speed and storage capacity. Parallel processing does not affect what a computer can or can't do: it's just a tactic which may allow some additional speed. It doesn't always have even that advantage - some tasks cannot be done in parallel anyway.

The visual system is often quoted as the best example of parallel processing, but what this seems to refer to is the existence of separate channels in which different kinds of feature recognition take place simultaneously: one dealing with colour, another with location in space, for example. This kind of activity certainly justifies the description 'parallel processing' in one sense, but not at all in the sense which implies a resemblance to parallel-processing computers. Moreover, while this kind of parallelism occurs in the visual and certain other systems, it is not typical of brain processes overall, and there are, so far as I know, no parallel channels which could plausibly be associated with conscious processes.

Another reason for talking about parallel processing seems to be the way a set of widely-separated sections of the cortex may be activated by a particular conscious experience. You could fairly say that these different sections were responding in parallel, but it looks more like the whole of the cortex being available for use in any single task. Certainly there is no sign here of the segregation of processes characteristic of parallel processing. 

It seems likely that part of the appeal of the 'massively parallel' idea stems from a confusion with the 'pandemonium' or 'multiple drafts' kind of theory, in which different potentially conscious threads of thought develop separately and compete for dominance. But the existence of these multiple threads at the conscious, or potentially conscious level, would imply nothing about parallelism at the operating level. Even Roger Penrose seems prey to this misconception when in 'The Emperor's New Mind' he seems to assume that parallel processing would necessarily involve thinking consciously about two different things at once. But suppose we had a program, running which gave rise to consciousness. Running it on a serial processor and running it on a parallel processor would achieve exactly the same result (possibly a little quicker on the parallel processor). Running it on a parallel processor would no more give rise to multiple consciousness than solving a problem with a parallel processor gives rise to multiple answers.

Daniel Dennett presents an intriguing argument in 'the Intentional Stance' about why the brain's supposed parallelism might give it a vital turn of speed that computers can never match (which might mean computers can never handle typical human tasks at real-time speeds - an uncharacteristically downbeat thought). There's something weird going on here: it's being suggested that the brain works in the same way that some powerful computers do, and that this is a way of working that computers may not be able to manage, and that therefore they might not be able to keep up with the brain - I think I must have misunderstood somewhere.  Even less fathomably, in 'Consciousness Explained', Dennett suggests consciousness might involve a parallel processor implementing a virtual serial processor. What would be the point of that?


A computer home

Blandula  People are always asserting that the brain is a computer. The comparison goes back to the days of Babbage, and in a sense, mechanical brains are exactly what computers were always supposed to be. It's only natural that people look for analogies (when I was young - well, younger - they used to compare the brain to a telephone switchboard) and computers are the obvious choice. In fact, however, there are no good analogies in the case of the brain. It is sui generis - utterly unlike anything else in the world (except another brain), and it differs fundamentally from a digital computer.

For one thing, the brain has no software. Universality is one of the essential characteristics of a computer - allowing for limitations of speed and storage, any computer can implement any function. By contrast, there is no way to load arbitrarily chosen new programs into the operating level of the brain: what it does is largely hard-wired. There is a degree of plasticity which allows it to recover from injury, and an ability to modify behaviour through learning: but neither resemble the loading of a new program. Only at the conscious level, at a painfully slow rate, can the brain 'run' programs. In addition, the brain is not a discrete-state machine. Computers, ideally, switch from one definite state to another with no transition. No real object behaves exactly like that in practice, but brains don't even come close, relying on a maze of interconnected physical and chemical processes none of which is instant. Now it can be argued, I realise, that the function of neurons is exactly to reduce this chaos to binary signals - either a neuron fires or it doesn't, after all - but the rate of firing and the complex series of events which determine it are not digital. I would add as a third point that computers are artefacts, while brains generate themselves - an important distinction.

Gerald Edelman stresses that the brain is not a computer: no two brains are wired the same way, he points out, and reality is not a program. Although there are counter-arguments, I think these are essentially sound points which draw attention to the falseness of the computer paradigm.

Curiously, John Searle , the leading sceptic about the possibility of generating consciousness by running a program, accepts that the brain is a computer. Latterly, however, he has argued that virtually everything in the world can be counted as a computer, including, for example a window. Now it is perfectly true that you can in theory interpret anything as being anything else if you're perverse enough. But for rational beings the choice of interpretation is not arbitrary. One minimum condition is surely that the thing you're interpreting as an X must do most of the work of being an X -  not the rules you apply in your interpretation. In order to use, say, a window as a computer, you need interpretive rules which effectively do all the computing themselves.


Illusory self home

 Blandula More than one author has come to the conclusion that the self is an illusion, but so far none of them has refused royalties on that account.  Scepticism about the reality of the self comes naturally to some materialists because of the historical association of  selfhood with belief in the soul and hence with dualism (denial of the self is also, on the other hand, an important doctrine of Buddhism, which aims to dispel the illusion), but it's one of those 'Sunday best' theories that no-one actually adopts, or could adopt, in real life: indeed, when applied to one's own self, it comes close to self-contradiction. I believe there is no self; it follows that there is no 'I'; and it follows that nobody believes that there is no self.

Why does this view, which surely runs strongly contrary to all our intuitions, appeal to some people? I think one reason is the strongly analytical tendency of the modern mind. We tend to look for final explanations at an atomic level, or at least in the disassembled parts of any mechanism. But by the time we've got down to working out how individual neurons work, we're already gone below the level where the self could reasonably be expected to be recognisable. It ought not to be too difficult to see through this confusion  (we don't say 'That's just a collection of cogs and springs - this clock you're talking about is an illusion', after all), but our intuitions tell us the self is unified and indivisible: so we feel that if it's anywhere it ought to be lying on the bench among the other dismantled pieces. Actually, of course, the fact that something is constituted or composed of parts doesn't stop it being a real, unified entity at the same time. 

By labelling the self as an illusion, of course, people do not necessarily mean to say that it has no existence at all; only that it is something other, and lesser, than what it appears to be. In particular, what is meant is that we are not the real source of our own decisions or behaviour - we just think we are (a kind of epiphenomenalism). Such a view might rest on straightforward determinism, reinforced by findings such as those of Benjamin Libet , but it is often reinforced by the observation that our conscious thoughts seem to come into our minds from nowhere: you can't catch yourself deciding to think something, however quickly you turn round.

There is really nothing mysterious about this. The processes which give rise to conscious thoughts cannot themselves be conscious, or they in turn would need to be underpinned by other conscious processes, and so on. The act of making a decision must always precede, if only marginally, conscious awareness of having made a decision. Discussions of Libet's research tend to assume that if a decision is conscious there must be immediate consciousness of the decision, but the two are actually distinct. Some would disagree, of course; some theories make a second-order awareness of conscious thoughts the very thing that makes them conscious: Libet's results perhaps are a real problem for those who take this view.

Ultimately, the fact of selfhood, and the moral agency and responsibility it supports, are features of the world which are just too salient to be denied: the task is not to debate their existence, but explain their nature.


There is something it is like home

Holy ineffability!
Bitbucket  This innocent-looking little phrase, which I believe comes from Nagel's famous paper 'What is it like to be a bat?' (summary of the paper - 'how would I know?') has played a quite astonishing role in raising the morale of the lovers of qualia. Whenever they're on the brink of throwing in the towel and admitting that it's been confused nonsense all along, they repeat the mantra and everyone brightens up again. The idea is that when you see something red, it isn't just a matter of acquiring some information about the light hitting your eye: there is something it is like to see the colour red.

To me, this is about as sensible as trying to include carnal knowledge in epistemology, or debating the ontology of the 'it' that does the raining. (Come to think of it, some idle philosopher has probably done that last one). When we talk about a thing being like something, that's what we mean - it's like something else. If I eat ostrich, and someone asks me what it's like, I don't screw up my face and say 'Uh, well I can't tell you, but there was an ineffable experience which it was like'. I say 'A bit like beef, with a slightly less granular texture.'

So, if there is something it is like to see red, what is it? Seeing puce?