I'm struggling with this one...how to begin?
You've got to hand it to me, trying to get a handle on this topic- if you're being even handed. Or at least give me a helping hand, or a big hand for my efforts.
Maybe I'll just give up and talk to the hand, listen to the sound of one hand clapping, ask for her hand in marriage (even though she's a handful) before the situation gets out of hand, walk with her hand-in-hand or, better still, since I've only been a hand (labourer) I'll just seek the Right Hand of God. Yes, always good to have that option in hand, up my sleeve, as it were.
As an old hand I know the truth is readily there, at hand, but how to begin? There are things that are concealed from my right hand...
Voltaire said of Sir Isac Newton that with all his science he knew not how his hand moved.
No point writing this blog, I'll have no further hand in it and no-one can grasp it. I reach for my tea....
What appears to be a spontaneous act is the most complex of things-if one thinks of it!
1. I locate the object in three dimensions. I must recognize it as the object. (let us put to one side how I got to be sitting here in the first place). For that I must also recognize myself as the subject who will reach out.
2. I need precise locations , but also some precise estimate of its size, weight, texture, whether it is hot or lukewarm.
3. This representation must now be translated into the 'appropriate set of joint angles for shoulder, elbow, and wrist: the sensorimotor transformation problem'. [what is this representation but a hybrid space between my own and that of the world? Are the 0,0,0 co-ordinates my hand, my arm, or my intentions?]
4. Of all the possible trajectories one must be chosen. How many are there? Is there an excess of freedom here? Is there a programme or a set of programmes that we must be able to continuously modify (questions of mechanism and free will arise here) or do we have absolute free choice? What determines that choice? Efficiency and economy of movements or, perhaps , culture?
5. Transporting the hand: there are typical velocity profiles that we work with and they follow a bell curve, slowing down as the hand approaches the tea. The muscle forces that will achieve the desired trajectory (whatever it is) have to be 'computed' (the inverse dynamics problem).
6. Is there one act of will involved or continuous acts of will over the distance between me and the tea? Even assuming perfectly static conditions and frames of reference, even assuming I am not distracted by the sounds and sights around me, or troubled by the memory of not being able to write a blog about the hand, the arm does not have a free hand, as it were, and counter-acting torques have to be taken into account: the reaching hand has to be reined in.
7. So, during the process of reaching each part of the body: arm--wrist-hand-fingers- is continuously re-adjusting both with respect to the other parts and to the space it is covering.
8. Pre-shaping of the hand: Even before the object is reached the hand takes on the appropriate shape. What is involved in this?
a) visual judgement of the size of the object and its relation to the size of the hand.
b) co-ordination of that visual information with motor co-ordination.
c) anticipatory control of the grip force appropriate to the object.
How is the ventral tract in the nervous system (responsible for cognition of shape, size, colour) related to the dorsal tract: responsible for moment -to-moment information on location and distribution of objects?
c) the relevant posture and grip force are, t is thought, modelled in the cerebellum ; the model is implemented and adjust for feedback.
That the hand is also responsible for knowing the world and guiding action -and not just manipulating the world, mechanically carrying out actions from some sort of programme, that in addition to this the hand is also communicative (both through gestures and writing), that these gestures then get ritualised into culture, leads one to the conclusion that it is truly, but not uniquely, quite amazing. Evolution? Yeah, right. V
Anyway, my tea is cold now...
1 comment:
I once wrote a poem consisting of only two words: Hands birds
Hands is an image. Birds is an image. Between them, a long wordless flight. Each reverberates in the stillness. The reverberations intermingle. In the centre one begins to pick up the interacting waves of sound and picture. The winged limb at rest and at full stretch. Agility, grace, efficiency, versatility, the power of the small: man's hand; birds. How one may hold another hand in one's own, like a bird, warm soft and perishable, it is held in trust. How one may hold a bird in one's hand, and feel the tender beating savage presence; through all the tenderness one feels as well the predatory claw, the blast off flight, the endurance, the skill.
One could muse forever on hand and bird, how they are similar and different. How they participate in the being of earth, both creatures of a feathered god with a thousand arms.
How hard it is to say anything about the poem without as it were putting handcuffs on the hands and tethers on the birds. If however one utters the word "hands" and then moves in its wake through the stirring stillness to "birds", and the two notes then work their magic simultaneously, the poem begins to live, and to do its work in the listening ear. There is really nothing to say, there is a mood in which quiet meditation seems most full of meaning.
Hands birds
Out of such a mood of speechlesness the poem was formed .
In the crisis to which life compels us, we search for the form by that which we may best join the world. As we come into touch with other beings, we discover ourselves. This is precise. As I experience the presence of a tree or a field or a stream or another person or a tremor that runs through me with a force of its own, I know myself through that experience. If I turn my glance always inward, I will look into the dark. The dark is real and rich, and it is surely there. But I will know nothing about it by looking into it, for I will see nothing. I will see into the dark only if I look at you. Then the dark will stir, will be stirred by our friction; a light will float like a feather in that dark and my whole being will shake with the creation that then happens.
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