Mais les résultats doivent être attendus longtemps et il n'y a généralement pas de temps amoxicilline prix L'autre cas, c'est que l'achat d'un ou d'un autre antibiotique dans une pharmacie classique nécessite des dépenses matérielles considérables et pas toutes les personnes ne peuvent acheter des produits pharmaceutiques aussi coûteux.

Microsoft word - greymatter51.htm


Through a glass darkly: peering at the grey matter

Rupert Wegerif reviews two popular mind/brain books and asks if knowing about brain
science is useful for teaching thinking
How the Mind Works
Steven Pinker
Paperback - 672 pages new edition (25 February, 1999)
Penguin Books; ISBN: 0140244913
The Private Life of the Brain
Susan Greenfield
Paperback - 272 pages (1 March, 2001)
Penguin Books; ISBN: 0140264914
People have been thinking, thinking about thinking and teaching thinking for thousands of years without knowing anything much about how brains work. Recently however resources for teaching thinking have begun to include sections on the brain and brain experts are giving keynote speeches at teaching thinking conferences. But is there any connection between knowledge of brains and teaching thinking? I think that I am a pretty good driver but I do not know where the carburettor is in my car engine or what function it performs. In fact I cannot even remember the last time that I looked under the bonnet. I do not see any reason why knowing about engine bits would improve either my driving ability or my ability to teach others how to drive. Can this analogy be applied to the relationship between knowledge of brains and thinking or do brain experts know something that teachers of thinking need to know? At a recent teaching thinking conference one presenter quoted Stephen Pinker as an authority for saying that people do not think in ordinary language but in ‘mentalese'. This claim troubled me. If this really was a finding of the latest brain research it would have implications for teaching thinking. On reading Pinker’s best-selling blockbuster ‘How the Mind Works’ I realised that I had no good reason to worry just yet. His claim that the mind thinks in ‘mentalese’ is not a new discovery but one of the initial assumptions of what he calls the 'computational theory of mind' - an already quite old and much criticised idea in psychology. Pinker assumes that the brain is a computer and the mind is made up of the programmes that this computers runs. All thinking is therefore to be seen as data-processing or number crunching of one sort or another. Just as computers operate with a machine code so the brain, on this theory, must have its own machine code or what he calls ‘mentalese’. Writing in a seductively accessible style Pinker simply asserts this controversial theory without acknowledging the many problems that there are with it. Although he claims that the book is about the brain the only evidence he appears to offer that his model fits the way that the brain actually works is that of ‘reverse engineering’. This is the idea that if we can get a computer to simulate something that the brain does then that can tell us something about how the brain actually does it. For example if we can use machine code to programme a computer to apparently hold a conversation then that tells us about what our brains must be doing behind the scenes when we hold a real conversation. This argument from reverse engineering seems curiously circular. First we imagine that the mind is like a computer, then we look at how a computer would do something that the mind already does and finally we conclude from this that the mind must really be rather like a computer. Many counter-examples could be given to show the weakness of this argument. My computer screen for example displays the time on a circular clock face with a little hand and big hand. The time shown is much the same as the time shown on an old-fashioned spring-wound alarm clock but I know that behind the computer display there are no wheels but a purely digital process. This digital 'reverse engineering' of a clock is done with numbers and computer code and so it tells me nothing about how a real old-fashioned clock works with its coiled steel spring and escapement mechanism that regulate the turning of cog-wheels. To find out about how a clock works it is not enough to simulate its outputs on a computer - you have to open it up and look inside. Many would say that the same is probably true of the human brain. To his credit Pinker admits that his computational model of mind cannot offer any plausible account of the nature of 'sentience' or 'consciousness' which appears to be unique to organic brains. He writes that: 'there is something peculiarly holistic and everywhere-at-once and nowhere-at-all and all-at-the-same-time about the problems of philosophy'. And argues that this shows that we have not been adapted by evolution to deal with such deep problems and best leave them alone. I felt short-changed by this. The important element of thinking for me is not the sort of mechanical computations that machines can potentially do much better than I ever could, but precisely the sort of reflection in which consciousness, and even what feels like the expansion of my consciousness, seem to play an essential part. If Pinker can say nothing about consciousness then his claim in the title to explain ‘how the mind works’ is an empty boast. Susan Greenfield takes a radically different approach in her latest book The Private Life of the Brain. Greenfield is a neuro-chemist who has also written The Human Brain: a Guided Tour and presented a television series on the brain, Brainstory, for BBC2. Her new book begins with a survey of approaches to the brain so far. She is fairly dismissive of those, like Pinker, who seem to think that we have understood the brain if we can programme computers to do humanlike things. She writes of Pinker’s account of the mind that; ‘we are still left in the dark as to how we would ever compute a headache or the exhilaration of first love’. She also rejects as a fallacy the idea that the brain has a ‘code’ of some sort as in Pinker’s ‘mentalese’. She writes that measurable changes in the brain, whether electrical, chemical or physical, are just what they are and should not be viewed as a code that can be converted into some other kind of thing. Understanding just what brain events really are raises the problem of understanding subjective feelings and consciousness. To claim that such events are some sort of computer code is, she says, simply a way of trying to evade this ultimately unavoidable question. Greenfield uses drugs as a way to explore the links between objective physical changes in the brain and subjective feelings. Both prescribed drugs such as Prozac and proscribed drugs such as LSD are known to have certain effects on neurons and synapses, while at the same time their effects on how people feel and think can be experienced and described. Detailed descriptions of the connection between objective brain chemistry and subjective states of mind lead her to some interesting theories. She argues, for example, that pleasure is the basic emotion and is reduced by the growing complexity of the mind. This she thinks can explain the many attempts of civilised people to return the brain to a simpler state through activities that can overwhelm the mind with strong sensations - rave music, recreational drugs, bungy jumping and sex are the escapes she mentions most frequently. Greenfield tackles the, in Pinker's words, ‘peculiarly holistic and everywhere-at-once and nowhere-at-all and all-at-the-same-time’ notion of consciousness through a description of the formation of temporary assemblies of large numbers of neurons around a single centre, rather like the ripples that form on a pond if you throw in a stone. Consciousness, she claims, is a product of the interaction of the brain with the rest of the body and is closely linked to the chemicals of the hormone system that co-ordinate the activity of large numbers of neurons. Initial consciousness is purely emotional but as regular pathways are formed between groups of neurons a mind develops within the brain bringing with it the possibility of reflective self-consciousness. Greenfield argues that the amount of our consciousness varies on a continuum from ‘shallow’ to ‘deep’ and that the subjective experience of depth of consciousness is directly related to the size of the temporary neuronal assembly and inversely related to strength of emotion. I find this theory fresh and exciting but certainly not wholly convincing. At times she seems to want to explain all the variety of our inner world with just a handful of fairly crude notions such as the numerical size of neuronal assemblies or the strength of activation of stimuli. Fear, pleasure and mania all seem to be characterised by small neuronal assemblies, although in fear they turn over fast, while abstract thought and depression are characterised by large and relatively unchanging neural assemblies. On this model ‘reason’ must be associated with depression and ‘unreason’ with pleasure. But I can’t help feeling that she may well have missed something vital. When anomalies emerge in her schema, for example when what she calls ‘Buddhist meditation’ appears to share all the brain features of depression, yet is correlated with subjective pleasure, she appears to fall into ad hoc arguments to explain the problem away without adapting the theory. She admits that she does not really know all that is going on yet but that this is a good first stab at a possible theory that might lead to testable hypotheses and so to building better theory. To return to my original question: should the findings of brain science be used to guide the teaching of thinking? The fact that the two authors reviewed here, both of whom are often referred to as leading neuro-scientists, offer such different and even opposing accounts of how the brain work should send out warning signals. There are almost as many theories in this area as there are authors. I am particularly fond of the view championed by Roger Penrose, and discussed by Susan Greenfield in an appendix to her book, that understanding how the brain works must also involve us in quantum physics and understanding the ultimate nature of the material universe. Only through involving physics in this way can we hope to find a scientific response to the old philosophical conundrum that the brain is as much within the field of our consciousness as our consciousness can be said to be located within the brain. Another account not addressed by Pinker and Greenfield comes from the Russian tradition of Vygotsky and Luria and stresses the role in the development of consciousness of culture through the internalisation of language and communication. Each of the many possible accounts of how the brain really works might have some consequences for how we go about teaching thinking. However at this stage in our knowledge they are all little more than informed speculations. Techniques for observing brain behaviour are improving rapidly and may one day soon offer the possibility of serious experimental tests of the sort of theory put forward by Susan Greenfield. This is an exciting prospect. The downside of this otherwise valuable ferment of debate and research is that when highly qualified and respected scientists such as Pinker put forward their speculations in an arrogant way as if these were simply ‘true’ naïve readers might be fooled. For me the message of these books is that our best guide to the nature of thinking and how to teach thinking must remain what it has always been, the practical ‘inside’ knowledge that we can develop simply through thinking, and above all through thinking about thinking for ourselves.

Source: http://elac.ex.ac.uk/dialogiceducation/userfiles/Greymatter51.pdf

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