[Martin Taylor 931123 10:10]
(Bill Powers 931122.1315) and later (Tom Bourbon 931122.1711)
RE: J-curves.
The most important fact, which you mentioned only in passing, was
that Gibbs reversed the normal relationship between the control
movement and the arrangement of the lights. So the relationship
was opposite to the way the environment normally responded to
actions.
I didn't emphasize it because I don't think it was the case in the later
studies, for which I can't get hold of the reports. It may have been so
in them as well, but I think not.
I would really like to see the raw data from this experiment.
So would I. That's why I suggested that we might try to repeat the kind
of study he did, to see how reliable the J-curve effect is, under what
circumstances. Until we have data to play with, we can't use the J-curve
effect as a fact to be accounted for, as I noted when I suggested that
it might be a place to look for feedforward effects.
The way you report the result is this:
If the light that had been on was number 1, 3, or 5, the
initial movement was correctly directed and quickly setlled
near the "correct" location. But if the transition was 2->1 or
4->5, the initial movement was "often" (my word) in the wrong
direction, quickly corrected to move in the right direction.From this description, I learn that all subjects responded
correctly every time to the 1-3-5 positions, and that some of
them produced a J-curve for the 2->1 and 4->5 transitions, some
of the time. Do the raw data support this literal interpretation?
I don't know. The text seems to support this interpretation. What
more can I say? Let's try it out, with different emphases on speed
and accuracy, and different kinds of timing and probability constraints
on the presentations of the lights. One might be able to do this by
(a) varying the conditional probabilities of light x following light y,
(b) switching the light position as soon as the cursor stayed within a
defined range w of the target for a defined time t, and (c) varying w
and t. (I say "light", but of course a target of the kind you normally
use in your tracking studies would be just as appropriate.
A variant experiment might be interesting, arranging the lights around
the perimeter of a circle at the corners of a regular polygon. Using
variation (a), one might be able to change the initial direction of
a track. For example, if the lights usually went clockwise around
the circle, one would not expect any track movements to start toward
the centre, but if the sequence was usually in the form of a pentagonal
star one might expect few of the initial moves to be around the circle
circumference. This might be a more sensitive test than Gibbs's linear
array, which affords only a left-right dichotomy.
ยทยทยท
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(Tom Bourbon 931122.1711)
Tom asks about my understanding of Bill P's 4-D tracking study.
If I am right that you can control only what you perceive,
and that reorganization yields controllable perceptions, people who can
do the task effectively should have achieved some kind of a perception of
a four-dimensional object.How so? Am I missing someting? The person will see a 2D rendering of a 3D
projection of the 4D "object." The person will not perceive a 4D object. I
thought (perhaps incorrectly) that Bill's point in the demonstratiuon would
be that the person can *control* his or her perceptions by *manipulating*
(using, not controlling) dimensions that are unperceived, perhaps
unperceivable.
One of us is missing something. I thought that one of the main features
of PCT is that we construct with our PIFs perceptual signals that an outside
observer would interpret as abstract perceptions of the world, such as
configurations, relations, and so forth. We "see" intensities, and from
their spatial and temporal relations we construct all other perceptions,
up to and including such perceptions as "democracy," "beauty," and the like.
I thought that Bill's demo was to show that in the same way, by learning
to control a perception that was of a structure intrinsically 4-dimensional,
we could develop perceptual signals that corresponded to what an outside
observer would say was a 4-D structure abstracted from the temporal and
spatial interrelations of point intensity fluctuations. If one can do
this without controlling the 4-D variable, it would be interesting. If
one can readily learn to control it, the existence of the perceptual
signal correesponding to the 4-D variable has been demonstrated. (There
is a caveat--the subject might be controlling all the lower-level variables
that enter into the 4-D percept, rather than the percept itself. That
would have to be tested by disturbing the lower-level variables individually
and seeing whether the disturbance to them or to the 4-D variable was
resisted.)
Martin