[Eetu Pikkarainen 2017-11-01]
(at the risk to be ridiculed )
I should be but as a humanist, I try not to be ashamed because of missing mathematical competence. I practice my understanding
by composing a non-mathematical description of what is going on in this case of PCT and Power Law.
When a living being is producing a movement trajectory by moving itself (e.g. crawling) or its organs (e.g. hand in a
drawing task) there seems to be a certain dependence between the curvature of the trajectory (proceeding straight or turning to some direction) and the speed/velocity (understood here as a moved distance along the trajectory during a time unit). The normal
case is that the speed is stable on the straight line but it slows down in a curve.
Now the first question is why that slowdown in the curve takes place. The second question is why the dependence between
curve and speed has those certain values, which have been observed in different situations. That latter question will be postponed.
PCT view is generally that the behavior of an organism is that it controls its certain perception(s) by affecting by its
output some environmental correlates of those perceptions. So when an organism is moving it can be controlling for its distance from some object to be long (if the object is perceived as dangerous) or short (if the object is perceived as desirable). Any regularities
of behavior are often assumed to be side effects of control. (Not side effects of observation.)
At the moment I have no idea what the larvae are controlling in those experiments but introspectively I can imagine some
possible perceptions I would control in a drawing task. First, I control seeing me a helpful aid in science making and being an obedient test subject and following to the rules. Then I would control to see the pen moving in a calm and nice way on the paper.
At the same time, I control that the pen follows the guiding line as strictly as possible. I think that my output function is such that it is easier to follow a line with certain kind of curvature than with another kind. We humans get much practice to draw
just certain kind of lines when we learn to draw and write. But there can also be some more general reasons why we use just those curves in our letters and typical drawings that we use. Anyway, it feels much more natural to draw a circle or looped circles
than rounded polygons.
Therefore, the increased difficulty in controlling of the latter perception (following the line) would draw some effort
away from the control of the first perception (keeping the steady or moderate speed). Or rather the slowing down the speed will make it easier to control the following the line. (A straight line is easier to draw with higher speed than very slowly.) So the
slowdown could be a side effect of control. Perhaps something similar is going on with larvae? Is it easier for them to go straight forward? Is it an additional challenge to turn to decide to turn and not to continnue forward? Would the slowdown make it easier
to control the perception of the new direction?
Is that at all where the PCT view of Power Law could begin?
Eetu
···
From: Alex Gomez-Marin [mailto:agomezmarin@gmail.com]
Sent: 31. lokakuuta 2017 18:01
To: Alex Gomez-Marin agomezmarin@gmail.com; csgnet@lists.illinois.edu
Subject: Re: The speedâ?curvature power law of movements: a reappraisal
regardless of your helicopter data and RCT mantras, it would be good if someone from CSGnet took seriously the challenge to PCT that the speed-curvature power law entails.
any figure panel of our paper proves rick’s mathematical claims wrong: the PL is not a must and when it takes place it is not trivial and can have different exponents.
now, how can “control of perception” explain that phenomenon? claiming it is an illusion because it does not fit in the dogma is like creationists insisting that dino fossils are bogus.
so, as adam and myself take this job seriously, and given how many optimal control and nonPCT theories explain the data, I think Bill would really find his edifice crumbling, or at least unable. so, take your best shot at it and really
challenge your “revolutionary paradigm changing” theory of behavior.
On Sun, 29 Oct 2017 at 02:48, Richard Marken rsmarken@gmail.com wrote:
[From Rick Marken (2017.10.28.1745)
On Sat, Oct 28, 2017 at 3:34 PM, Alex Gomez-Marin agomezmarin@gmail.com wrote:
attached
RM: Finally! Thank you, Alex. I hope the journal gives us an opportunity to respond. But for now I have only one word for you: helicopter movements. Oh, that’s two words But you know how bad I am at math;-)
Best
Rick
–
Richard S. Marken
"Perfection is achieved not when you have nothing more to add, but when you
have nothing left to take away.â?
--Antoine de Saint-Exupery
–
Alex Gomez-Marin