[Martin Taylor 920318 16:30]
(Bill Powers 920318 08:00)
We've gotten a bit off the track
by talking about how you can detect controlled variables when the reference
level is randomly changing, using statistical methods like Marken's "mind-
reading" demo. That's really doing things the hard way. While we may
eventually have to do things the hard way, right now there are plenty of
aspects of behavior we can study in which there aren't large unpredictable
changes in reference signals -- especially if we design experiments to
avoid them. In that kind of experiment, the statistical treatment is
unnecessary, except to satisfy those who don't believe data unless they can
see a correlation and a confidence level.
By doing experiments with fixed reference levels, I think you are leaving
yourself wide open to an S-R interpretation. If in an ECS the reference
level is fixed, then the "stimulus" percept does determine the error signal
and thus the observed behaviour. That there are disturbances to be
compensated for is clear, but interpretable as behaviour that is a
consequence of the disturbing stimulus.
Separate comment on the same paragraph:
Statistical treatment is avoidable only if you have almost correctly guessed
what percept is being controlled and, perhaps more important, what effects
your experimentally induced disturbances would have if the subject were
not controlling. If you are in error in either of these, you are in trouble
without statistics. But I agree with you that "confidence levels" are an
abomination, though my reasons are quite different.
And I don't think you should believe that psychologists are unaware of the
effects of correlation (negative or positive) on the variance of joint
phenomena.
To change the subject: is no-one interested in my argument that the degrees
of freedom problem leads to modular reorganization, or did it not get out
to the list?
Also, no-one has made any suggestions in respect of my Paris talk, which was
sent at around the same time, which makes me think that perhaps neither item
got distributed (and perhaps others as well). I would think Paris is an
opportunity to put the PCT case before a reasonably influential audience,
and you would like the opportunity to suggest lines of attack.
Martin