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Being selfish
The last word Being selfish John McCrone http://www.btinternet.com/~neuronaut/
Oww! I just bit my tongue. What a dumb thing to do. Well actually, when you think about it, chewing great mouthfuls of food at high speed while concentrating on other important stuff, like reading the morning paper, is just about the single most impressive neurological feat that there is. Amidst flashing molars and incisors, the muscles of the tongue, lips and cheek deftly manipulate a bolus of soggy paste. The lumpy bits get sifted and positioned for further chomping. Then the mass is shaped at the back of the mouth ready for the convulsive act of swallowing. It is not just the snazzy motor control that allows our tongue to dance barely millimetres from bloody disaster. It is the way the brain can create such a sharply defined sense of self and not-self in the cramped, sticky confines of the mouth. The sensory difference between mushed cereal and the writhing muscles of the tongue seems astonishingly slight. But confusion happens so rarely that we feel almost guilty, a need to apologise to our own tongue, when it gets a nip in the course of its work. The sense of self is one of the great philosophical conundrums. Who is the “I” that does all the feeling, sensing and willing? Many have treated this as a deep logical problem. If there is a self inside the head—a homunculus that is the target of subjective experience—then it must have a smaller observer tucked away inside its head, and so on ad infinitum. But recently consciousness researchers have been returning to the much more pragmatic view of William James, treating the self as simply a context that makes its presence known by the way it shapes the flows of neural activity. Selfhood is not to be found in some special brain bump (such as the anterior cingulate cortex). Rather, like the way the gouged-out banks of a river give shape to the flows of the stream, the sense of self reflects the shape of the vessel—an accumulation of all the tiny cognitive habits and routines distributed across the nervous system. Perhaps the most vigorous proponent of the view that selfhood is a globally-produced systems property was the Chilean neuroscientist, Francisco Varela, who sadly died, aged 54, last year. Along with fellow Chilean, Humberto Maturana, Varela argued that even the immune and
330
endocrine systems are “cognitive” and work by being able to distinguish self from non-self. So the identity of a living organism is not some abstract high level process but embodied at every level of its operation. The ability to chew only the food in our mouths, and not other things like tongues, is a perfect example. Exactly how we achieve this feat is a complex story. Obviously, forward models of motor control and reafference messaging are central to the explanation. We know our tongue because we form precise, if usually subconscious, mental predictions of its every action. The food is then the stuff that is not under this kind of motor control. The fine tolerances achieved during chewing would owe a lot to sensory acuity. The lips and tongue are about twice as sensitive as the fingertips—which is why holes drilled by the dentist feel so enormous before they are filled. The rather inglorious phenomenon of mouth stuffing makes plain that chewing is a skill that has to be learned, only later turning into an unremarked habit. Kids at age two delight in cramming as much food into their mouths as possible. Psychologists say this maximises the sensory feedback from the act of eating, helping them eventually to establish the more efficient—and less disgusting—habits that their parents desire. But sensorimotor disorders can lead to this behaviour persisting. Children with poor oral discrimination will keep stuffing. After meals, food may even be left unnoticed lodged on the palate, where it can later drop to cause choking. Other children have mouths that are hypersensitive so they stuff because they find the unpredictable movement of small bits of food too nerve-wracking. Our ability to divide the world into self and not-self, to construct boundaries, is obviously a remarkable mental accomplishment. Mind researchers like to use the strange and bizarre to point this out—neglect syndromes, out of body states, the distorted body image of anorexics, the thought insertion of schizophrenics, the phantom limbs of amputees. But just for today, let’s hear it for the tongue and that largely unheralded skill, mastication. Right then, tongue? Am I forgiven yet?
THE LANCET Neurology Vol 1 September 2002
http://neurology.thelancet.com
For personal use. Only reproduce with permission from The Lancet Publishing Group.
Oww! I just bit my tongue. What a dumb thing to do. Well actually, when you think about it, chewing great mouthfuls of food at high speed while concentrating on other important stuff, like reading the morning paper, is just about the single most impressive neurological feat that there is. Amidst flashing molars and incisors, the muscles of the tongue, lips and cheek deftly manipulate a bolus of soggy paste. The lumpy bits get sifted and positioned for further chomping. Then the mass is shaped at the back of the mouth ready for the convulsive act of swallowing. It is not just the snazzy motor control that allows our tongue to dance barely millimetres from bloody disaster. It is the way the brain can create such a sharply defined sense of self and not-self in the cramped, sticky confines of the mouth. The sensory difference between mushed cereal and the writhing muscles of the tongue seems astonishingly slight. But confusion happens so rarely that we feel almost guilty, a need to apologise to our own tongue, when it gets a nip in the course of its work. The sense of self is one of the great philosophical conundrums. Who is the “I” that does all the feeling, sensing and willing? Many have treated this as a deep logical problem. If there is a self inside the head—a homunculus that is the target of subjective experience—then it must have a smaller observer tucked away inside its head, and so on ad infinitum. But recently consciousness researchers have been returning to the much more pragmatic view of William James, treating the self as simply a context that makes its presence known by the way it shapes the flows of neural activity. Selfhood is not to be found in some special brain bump (such as the anterior cingulate cortex). Rather, like the way the gouged-out banks of a river give shape to the flows of the stream, the sense of self reflects the shape of the vessel—an accumulation of all the tiny cognitive habits and routines distributed across the nervous system. Perhaps the most vigorous proponent of the view that selfhood is a globally-produced systems property was the Chilean neuroscientist, Francisco Varela, who sadly died, aged 54, last year. Along with fellow Chilean, Humberto Maturana, Varela argued that even the immune and
330
endocrine systems are “cognitive” and work by being able to distinguish self from non-self. So the identity of a living organism is not some abstract high level process but embodied at every level of its operation. The ability to chew only the food in our mouths, and not other things like tongues, is a perfect example. Exactly how we achieve this feat is a complex story. Obviously, forward models of motor control and reafference messaging are central to the explanation. We know our tongue because we form precise, if usually subconscious, mental predictions of its every action. The food is then the stuff that is not under this kind of motor control. The fine tolerances achieved during chewing would owe a lot to sensory acuity. The lips and tongue are about twice as sensitive as the fingertips—which is why holes drilled by the dentist feel so enormous before they are filled. The rather inglorious phenomenon of mouth stuffing makes plain that chewing is a skill that has to be learned, only later turning into an unremarked habit. Kids at age two delight in cramming as much food into their mouths as possible. Psychologists say this maximises the sensory feedback from the act of eating, helping them eventually to establish the more efficient—and less disgusting—habits that their parents desire. But sensorimotor disorders can lead to this behaviour persisting. Children with poor oral discrimination will keep stuffing. After meals, food may even be left unnoticed lodged on the palate, where it can later drop to cause choking. Other children have mouths that are hypersensitive so they stuff because they find the unpredictable movement of small bits of food too nerve-wracking. Our ability to divide the world into self and not-self, to construct boundaries, is obviously a remarkable mental accomplishment. Mind researchers like to use the strange and bizarre to point this out—neglect syndromes, out of body states, the distorted body image of anorexics, the thought insertion of schizophrenics, the phantom limbs of amputees. But just for today, let’s hear it for the tongue and that largely unheralded skill, mastication. Right then, tongue? Am I forgiven yet?
THE LANCET Neurology Vol 1 September 2002
http://neurology.thelancet.com
For personal use. Only reproduce with permission from The Lancet Publishing Group.