Archive for July, 2011

Picture: Raymond Tallis‘Aping Mankind’ is a large scale attack by Raymond Tallis on two reductive dogmas which he characterises as ‘Neuromania’ and ‘Darwinitis’.  He wishes especially to refute the identification of mind and brain, and as an expert on the neurology of old age, his view of the scientific evidence carries a good deal of weight. He also appears to be a big fan of Parmenides, which suggests a good acquaintance with the philosophical background. It’s a vigorous, useful, and readable contribution to the debate.

Tallis persuasively denounces exaggerated claims made on the basis of brain scans, notably claims to have detected the ‘seat of wisdom’ in the brain.  These experiments, it seems, rely on what are essentially fuzzy and ambiguous pictures arrived at by subtraction in very simple experimental conditions, to provide the basis for claims of a profound and detailed understanding far beyond what they could possibly support. This is no longer such a controversial debunking as it would have been a few years ago, but it’s still useful.

Of course, the fact that some claims to have reduced thought to neuronal activity are wrong does not mean that thought cannot nevertheless turn out to be neuronal activity, but Tallis pushes his scepticism a long way. At times he seems reluctant to concede that there is anything more than a meaningless correlation between the firing of neurons in the brain and the occurence of thoughts in the mind.  He does agree that possession of a working brain is a necessary condition for conscious thought, but he’s not prepared to go much further. Most people, I think, would accept that Wilder Penfield’s classic experiments, in which the stimulation of parts of the brain with an electrode caused an experience of remembered music in the subject, pretty much show that memories are encoded in the brain one way or another; but Tallis does not accept that neurons could constitute memories. For memory you need a history, you need to have formed the memories in the first place, he says: Penfield’s electrode was not creating but merely reactivating memories which already existed.

Tallis seems to start from a kind of Brentanoesque incredulity about the utter incompatibility of the physical and the mental. Some of his arguments have a refreshingly simple (or if you prefer, naive) quality: when we experience yellow, he points out, our nerve impulses are not yellow.  True enough, but then a word need not be printed in yellow ink to encode yellowness either. Tallis quotes Searle offering a dual-aspect explanation: water is H2O, but H2O molecules do not themselves have watery properties: you cannot tell what the back of a house loks like from the front, although it is the same house. In the same way our thoughts can be neural activity without the neurons themselves resembling thoughts. Tallis utterly rejects this: he maintains that to have different aspects requires a conscious observer, so we’re smuggling in the very thing we need to explain.  I think this is an odd argument. If things don’t have different aspects until an observer is present, what determines the aspects they eventually have? If it’s the observer, we seem to slipping towards idealism or solipsism, which I’m sure Tallis would not find congenial. Based on what he says elsewhere, I think Tallis would say the thing determines its own aspects in that it has potential aspects which only get actualised when observed; but in that case didn’t it really sort of have those aspects all along? Tallis seems to be adopting the view that an appearance (say yellowness) can only properly be explained by another thing that already has that same appearance (is yellow). It must be clear that if we take this view we’re never going to get very far with our explanations of yellow or any other appearance.

But I think that’s the weakest point in a sceptical case which is otherwise fairly plausible. Tallis is Brentanoesque in another way in that he emphasises the importance of intentionality – quite rightly, I think. He suggests it has been neglected, which I think is also true, although we must not go overboard: both Searle and Dennett, for example, have published whole books about it. In Tallis’ view the capacity to think explicitly about things is a key unique feature of human mindfulness, and that too may well be correct. I’m less sure about his characterisation of intentionality as an outward arrow. Perception, he says, is usually represented purely in terms of information flowing in, but there is also a corresponding outward flow of intentionality. The rose we’re looking at hits our eye (or rather a beam of light from the rose does so), but we also, as it were, think back at the rose. Is this a useful way of thinking about intentionality? It has the merit of foregrounding it, but I think we’d need a theory of intentionality  in order to judge whether talk of an outward arrow was helpful or confusing, and no fully-developed theory is on offer.

Tallis has a very vivid evocation of a form of the binding problem, the issue of how all our different sensory inputs are brought together in the mind coherently. As normally described, the binding problem seems like lip-synch issues writ large: Tallis focuses instead on the strange fact that consciousness is united and yet composed of many small distinct elements at the same time.  He rightly points out that it’s no good having a theory which merely explains how things are all brought together: if you combine a lot of nerve impulses into one you just mash them. I think the answer may be that we can experience a complex unity because we are complex unities ourselves, but it’s an excellent and thought-provoking exposition.

Tallis’ attack on’ Darwinitis’ takes on Cosmidoobianism, memes and the rest with predictable but entertaining vigour. Again, he presses things quite a long way. It’s one thing to doubt whether every feature of human culture is determined by evolution: Tallis seems to suggest that human culture has no survival value, or at any rate, had none until recently, too recently to account for human development. This is reminiscent of the argument put by Alfred Russel Wallace, Darwin’s co-discoverer of the principle of survival of the fittest: he later said that evolution could not account for human intelligence because a caveman could have lived his life perfectly well with a much less generous helping of it. The problem is that this leaves us needing a further explanation of why we are so brainy and cultured; Wallace, alas, ended up resorting to spiritualism to fill the gap (we can feel confident that Tallis, a notable public champion of disbelief, will never go that way). It seems better to me to draw a clear distinction between the capacity for human culture, which is wholly explicable by evolutionary pressure, and the contents of human culture, which are largely ephemeral, variable, and non-hereditary.

Tallis points out that some sleight of hand with vocabulary is not unknown in this area, in particular the tactic of the transferrred epithet: a word implying full mental activity is used metaphorically – a ‘smart’ bomb is said to be ‘hunting down’ its target – and the important difference is covertly elided. He notes the particular slipperiness of the word ‘information’, something we’ve touched on before.

It is a weakness of Tallis’ position that he has no general alternative theory to offer in place of those he is attacking – consciousness remains a mystery (he sympathises with Colin McGinn’s mysterianism to some degree, incidentally, but reproves him for suggesting that our inability to understand ourselves might be biological). However, he does offer positive views of selfhood and free will, both of which he is concerned to defend. Rather than the brain, he chooses to celebrate the hand as a defining and influential human organ: opposable thumbs allow it to address itself and us: it becomes a proto-tool and this gives us a sense of ourselves as acting on the world in a tool-like manner. In this way we develop a sense of ourselves as a distinct entity and an agent, an existential intuition.  This is OK as far as it goes though it does sound in places like another theory of how we get a mere impression, or dare I say an illusion, of selfhood and agency, the very position Tallis wants to refute. We really need more solid ontological foundations. In response to critics who have pointed to the elephant’s trunk and the squid’s tentacles, Tallis grudgingly concedes that hands alone are not all you need and a human brain does have something to contribute.

Turning to free will, Tallis tackles Libet’s experiments (which seem to show that a decision to move one’s hand is actually made a measurable time before one becomes aware of it). So, he says, the decision to move the hand can be tracked back half a second? Well, that’s nothing: if you like you can track it back days, to when the experimental subject decided to volunteer; moreover, the aim of the subject was not just to move the hand, but also to help that nice Dr Libet, or to forward the cause of science. In this longer context of freely made decisions the precise timing of the RP is of no account.

To be free according to Tallis, an act must be expressive of what the agent is, the agent must seem to be the initiator, and the act must deflect the course of events. If we are inclined to doubt that we can truly deflect the course of events, he again appeals to a wider context: look at the world around us, he says, and who can doubt that collectively we have diverted the course of events pretty substantially?  I don’t think this will convert any determinists. The curious thing is that Tallis seems to be groping for a theory of different levels of description, or well, a dual aspect theory.  I would  have thought dual-aspect theories ought to be quite congenial to Tallis, as they represent a rejection of ‘nothing but’ reductionism in favour of an attempt to give all levels of interpretation parity of esteem, but alas it seems not.

As I say, there is no new theory of consciousness on offer here, but Tallis does review the idea that we might need to revise our basic ideas of how the world is put together in order to accommodate it. He is emphatically against traditional dualism, and he firmly rejects the idea that quantum physics might have the explanation too. Panpsychism may have a certain logic but generate more problems than it solves.  Instead he points again to the importance of intentionality and the need for a new view that incorporates it: in the end ‘Thatter’, his word for the indexical, intentional quality of the mental world, may be as important as matter.

Picture: CorticothalamicThis paper on ‘Biology of Consciousness’ embodies a remarkable alliance: authored by Gerald Edelman, Joseph Gally, and Bernard Baars, it brings together Edelman’s Neural Darwinism and Baars’ Global Workspace into a single united framework. In this field we’re used to the idea that for every two authors there are three theories, so when a union occurs between two highly-respected theories there must be something interesting going on.

As the title suggests, the paper aims to take a biologically-based view, and one that deals with primary consciousness. In human beings the presence of language among other factors adds further layers of complexity to consciousness; here we’re dealing with the more basic form which, it is implied, other vertebrates can reasonably be assumed to share at least in some degree. Research suggests that consciousness of this kind is present when certain kinds of connection between thalamus and cortex are active: other parts of the brain can be excised without eradicating consciousness. In fact, we can take slices out of the cortex and thalamus without banishing the phenomenon either: the really crucial part of the brain appears to be the thalamic intralaminar nuclei.  Why them in particular? Their axons radiate out to all areas of the cortex, so it seems highly likely that the crucial element is indeed the connections between thalamus and cortex.

The proposal in a nutshell is that dynamically variable groups of neurons in cortex and thalamus, dispersed but re-entrantly connected constitute a flexible Global Workspace where different inputs can be brought together, and that this is the physical basis of consciousness. Given the extreme diversity and variation of the inputs, the process cannot be effectively ring-mastered by a central control; instead the contents and interactions are determined by a selective process – Edelman’s neural Darwinism (or neural group selection): developmental selection (‘fire together, wire together’), experiential selection, and co-ordination through re-entry.

This all seems to stack up very well  (it seems almost too sensible to be the explanation for anything as strange as consciousness). The authors note that this theory helps explain the unity of consciousness.  It might seem that it would be useful for a vertebrate to be able to pay attention to several different inputs at once, thinking separately about different potential sources of food, for example: but it doesn’t seem to work that way – in practice there seems to be only one subject of attention at once; perhaps that’s because there is only one ‘Dynamic Core’.  This constraint must have compensating advantages, and the authors suggest that these may lie in the ability of a single piece of data to be reflected quickly across a whole raft of different sub-systems. I don’t know whether that is the explanation, but I suspect a good reason for unity has to do with outputs rather than inputs. It might seem useful to deal with more than one input at a time, but having more than one plan of action in response has obvious negative survival value. It seems plausible that part of the value of a Global Workspace would come from its role in filtering down multiple stimuli towards a single coherent set of actions. And indeed, the authors reckon that linked changes in the core could give rise to a coherent flow of discriminations which could account for the ‘stream of consciousness’.  I’m not altogether sure about that – without saying it’s impossible a selective process without central control can give rise to the kind of intelligible flow we experience in our mental processes, I don’t quite see how the trick is done. Darwin’s original brand of evolution, after all, gave rise to speciation, not coherence of development. But no doubt much more could be said about this.

Thus far, we seem on pretty solid ground. The authors note that they haven’t accounted for certain key features of consciousness, in particular subjective experience and the sense of self: they also mention intentionality, or meaningfulness.  These are, as they say, non-trivial matters and I think honour would have been satisfied if the paper concluded there: instead however, the authors gird their loins and give us a quick view of how these problems might in their view be vanquished.

They start out by emphasising the importance of embodiment and the context of the ‘behavioural trinity’ of brain, body, and world. By integrating sensory and motor signal with stored memories, the ‘Dynamic Core’ can, they suggest, generate conceptual content and provide the basis for intentionality. This might be on the right track, but it doesn’t really tell us what concepts are or how intentionality works: it’s really only an indication of the kind of theory of intentionality which, in a full account, might occupy this space.

On subjective experience, or qualia, the authors point out that neural and bodily responses are by their nature private, and that no third-person description is powerful enough to convey the actual experience. They go on to deny that consciousness is causal: it is, they say, the underlying neural events that have causal power.  This seems like a clear endorsement of epiphenomenalism, but I’m not clear how radical they mean to be. One interpretation is that they’re saying consciousness is like the billows: what makes the billows smooth and bright? Well, billows may be things we want to talk about when looking at the surface of the sea, but really if we want to understand them there’s no theory of billows independent of the underlying hydrodynamics. Billows in themselves have no particular explanatory power. On the other hand, we might be talking about the Hepplewhiteness of a table. This particular table may be Hepplewhite, or it may be fake. Its Hepplewhiteness does not affect its ability to hold up cups; all that kind of thing is down to its physical properties. But at a higher level of interpretation Hepplewhiteness may be the thing that caused you to buy it for a decent sum of money.  I’m not clear where on this spectrum the authors are placing consciousness – they seem to be leaning towards the ‘nothing but’ end, but personally I think it’s to hard to reconcile our intuitive sense of agency without Hepplewhite or better.

On the self, the authors suggest that neural signals about one’s own responses and proprioception generate a sense of oneself as a separate entity: but they do not address the question of whether and in what sense we can be said to possess real agency: the tenor of the discussion seems sceptical, but doesn’t really go into great depth. This is a little surprising, because the Global Workspace offers a natural locus in which to repose the self. It would be easy, for example, to develop a compatibilist theory of free will in which free acts were defined as those which stem from processes in the workspace but that option is not explored.

The paper concludes with a call to arms: if all this is right, then the best way to vindicate it might be to develop a conscious artefact: a machine built on this model which displays signs of consciousness – a benchmark might be clear signs of the ability to rotate an image or hold a simulation. The authors acknowledge that there might be technical constraints, but I think they an afford to be optimistic. I believe Henry Markram, of the Blue Brain project, is now pressing for the construction of a supercomputer able to simulate an entire brain in full detail, so the construction of a mere Global Dynamic Core Workspace ought to be within the bounds of possibility – if there are any takers..?