Tom on Taylor/Speer

[From Rick Marken (940405.1100)]

Tom Bourbon said I could go ahead and post these to the net; if copies of
them do show up later as repeats, well, sue me (but beware -- I'll retain
Martin Taylor as my lawyer).


Date: Mon, 4 Apr 94 08:50:22 CST
From: "Tom Bourbon" <>
Subject: Re: Derivatives and Clarifications

From Tom Bourbon [940404.0913]

<Martin Taylor 940401 18:00>

I've not been posting to CSG-L for some time, for two reasons. First is
the time taken by the ongoing sleep study, which leaves little time for
anything else. But now we will have two weeks rather than one to deal with
the run about to complete and to prepare for the next one, so things are
slightly relaxed. Enough, anyway for a few comments on items from the
last three or four weeks. The second reason is that I have been spending
a lot of time communicating and consulting with Bill P., both on the
tracking studies in the sleep deprivation experiment and on the matter of
information theory in the analysis and prediction of the behaviour of control
systems. We have not come to a common position, but I think we both
understand things a little differently from the way we did a month ago.
So I will not comment further on that yet.

Rick Marken (940310.2130)

But I am worried by the
request that Martin clarify his prediction if we misunderstood it. I can't
imagine a clearer claim (or prediction) than the one that Martin made
above ("But the derivatives [of perceptual signal and disturbance] are
not independent"). When we showed a plot indicating that these
derivatives ARE independent, Martin said that this result was
EXPECTED. So I can only presume that Martin's "clarification" of
the prediction of non-independece of the derivatives is that they ARE
independent. Is that clear?

Funny perception! I quote the data that you say shows the derivatives
to be independent:

       >Bill Powers (940302.1300 MST)
       >The correlation of the derivative of the disturbance with the
       >derivative of the delayed perceptual signal is 0.268.

That does not look to me to agree with your statement. The result that
was expected was that the correlation is positive and that it is not large.
The data look to me to be as expected. Still. The derivatives are
certainly NOT independent. Is that clear?


That certainly is clear, Martin. So, too, is the fact that for r = .268,
k = .963. ( k + sqrt (1 - r*r) ) For anyone who missed our discussions
of k a couple of years ago, back in the 50's and earlier it was pretty widely
known as the "coefficient of alienation." It should be a required element
in any manuscript that contains correlations and is submitted for
publication. (I imagine that its inclusion would reduce the number of
publications in behavioral, social, cognitive and brain science by about
99.8 percent.) In our nasty way, some of us on csg-l like to call it the
coefficient of uselesness. If r indicates the "strength of a relationship"
reflected in a correlation, k indicates the degree of lack of relationship.

All of that said, you are certainly right, Martin, when you say that the
derivatives are not independent; it's just that they aren't very dependent
-- the relationship is so weak that using it as a basis for predictions
would leave you with predictions that are 96.3 percent as likely to be in
error as they would have been if you didn't even know the correlation.
That, in spite of the fact that with n = 1800 or more pairs of predicted
and actual data values, even a correlation < .02 is astronomically
statistically significant. Significant, but trivial. Significantly
non-zero, but useless and meaningless.

Incidentally, if you look back at my post on time-lagged correlations
between variables in a simple pursuit tracking task, you'll see many
correlations in the range of .1 to .2 or so. What reason is there to
assume that one of those trivial, yet significant, correlations is more
meaningful than any other?



Date: Mon, 4 Apr 94 08:04:42 CST
From: "Tom Bourbon" <>
Subject: RE: A funny thing happened in sci.cognitive

From Tom Bourbon [940404.0843]

[From Rick Marken (940403.1130)]

Damn it, Rick. You just had to ruin my Monday morning, didn't you? I'd
just about forgotten the high regard in which PCT and I (and my many
students) were held by some of my former academic "colleagues" at SFA. :-))

I found this in the NewsNet group sci.cognitive. I can see why Tom
Bourbon's hair is all white (like mine). Who is this guy, Tom?
I'll wait a couple days before responding to see if anyone with a
cooler head than mine (ie. just about EVERYBODY) wants to handle
this first.



I'd suggest you take the first shot, and I invite anyone else who is
interested to join in the fun. I don't read the NewsNet and don't know
how to send a reply.

Article 3267 of sci.cognitive:


Newsgroups: sci.cognitive
Subject: Re: W. Powers' Perceptual Control Theory
Message-ID: <>
From: (James Speer)
Date: 28 Mar 94 16:49:26 CST
References: <>
Distribution: world
Organization: Stephen F. Austin State University

In article <>,

(Edmund Shing) writes:


Could someone please give me a brief summary of William Powers' Perceptual
Control Theory - I am about to get hold of his 1973 book "Behavior: The
Control of Perception", but wondered if I could get hold of a concise


first to enable me to see if it is relevant to my research interests
(Processes of associative learning and attention in intelligent agent

I believe a brief version appeared in Psych. Review about the same time the
book came out.

From what I have been told, his theory seems to bear relations to Gibson's
(1979) concept of "affordances", Ballard's (1991) animate vision paradigm


Heidegger's concept of "Dasein" (cf. Chapman, 1990).

If you're looking for CLOSE relations to the foregoing theories / ideas, I
think you're in for a disappointment. Powers' view, I have always thought, is
insufficiently constrained to count as a theory. A "meta-theory" or research
program, perhaps.



James R. Speer Phone: 409 568 1478
Department of Psychology Fax: 409 568 2190
Stephen F. Austin State University E-mail:

Nacogdoches TX 75962-3046 Ham Radio: K5YUT


I've erased about a dozen starts at some comments on this post. It's
probably best that I simply repeat my invitation for anyone who is
interested to send replies to Jim's message, which speaks volumes about the
level of his interest in and attention to my work while I was at SFA. He's
a "real" meta-meta cognitivist, in case you can't tell. You know them --
the people with the well-constrained theories. (Yuk!)