[Avery.Andrews 930126.0530]
Whether or not the arm demo is a piece of routine robotics or something
completely different, it does seem to me to be a flat-out refutation
of some ideas that psychologists (or at least kinesiologists) have
gotten from engineers, for example the Smith quote that Greg
Williams pulled out:
>210 - "Engineers can design robots and other machines to behave... using what
>they call POINT-TO-POINT COMPUTATION methods. The position of the limb at each
>point in space and at each time in the movement is represented by a reference
>for correctness, and the system can be made to track this set of positions
>across time to produce an action with a particular form. But the system must
>be very 'smart,' and it must process information very rapidly, even for the
>simplest of movements. All of these references for correctness must be stored
>somewhere, and each of the points will be different if the movement begins
>from a slightly different place or if it is to take a slightly different
>pathway through space.
(Still present in the 1988 edition, but on pg. 163)
The arm circuitry is of course very dumb, has no trouble in processing
the required information extremely rapidly, & it doesn't store references
for `correctness' in anything like the manner suggested (there is the
vkmap, but that's different). Schmidt doesn't cite any engineering
works, so I don't know where he got this idea from (though I've seen
it elsewhere, in a 1987 JMB article by Darling & Cooke, but maybe they
were just copying it off him).
The passage also illustrates many features of non-dynamical thinking -
it seems to be assumed that the `references for correctness' have to
be prefabricated and stored somewhere, rather than just spat out in
real time by a smoother, or perhaps some more sophisticted device,
and that they actually have to be attained, rather than just accelerated
towards.
Of course at this point I have no idea whether some engineers actually
thought along these lines, or whether psychologists misunderstood them,
but the consequences have clearly flowed through to the late 80s.
Avery.Andrews@anu.edu.au