Newsgroups: bit.listserv.csg-l
Date:         Sat, 10 Oct 1992 15:57:43 EDT
From:         "(Martin Taylor)" <mmt@BEN.DCIEM.DND.CA>
Subject: Re: Why 99%, hierarchical perception

[Martin Taylor 921010 15:40]
(Rick Marken 921009.1230)

This really has to be brief.  Sorry.

> What is the "variance of our estimates"
>by the way? What is the "residual variance" here? the variance of the
>the size of the quadrilateral relative to the reference size? In what
>way is the residual variance "constant" in log size or area units.

The residual variance is the 1% or 2% that you didn't account for. Since
the feedback loop function is the same for any level of the reference signal,
I assume that the error variance within the ECS, largely due to non-infinite
gain, is independent of the level of the reference signal, and that it is
a major contributor to the residual variance that you (experimenter) see.
>
> Maybe it's my bias but why not have the
>reference square vary continuously in size?

That would be better, because then you could determine the residual variance
as a function of size, and perhaps draw some tighter conclusions than my
two-point proposal would have allowed.


>>I think the results would be contaminated by other effects, but the main idea
>>should be valid.  It's a very simple kind of case, but it is typical of the
>>sort of thing that psychologists want to know.
>
>Yes, and they miss the whole point. The fact that the person is controlling
>a variable and that it took some doing to figure out what it is just goes
>right by. Early astronomers wanted to know how the patterns they saw in
>the night sky were related to one's personality. I know it's rude but,
>frankly, I could care less what conventional psychologists want to know.
>What they want to know is based on their preconceptions about how people
>work; so they think it is important to know how reinforcement affects
>behavior or which behavioral/cognitive capabilities are in the right
>brain and which are in the left, etc etc.

Well, I want to know how people work, even if you don't.  It isn't enough for
me to accept that behaviour is controlled perception.  I want to know where
the signals go (functionally), and what happens if you block this of that
path, how to deal with people suffering from stroke, why we have focussed
attention and what its limitations are, whether we use internal feedback
for short-term memory, and all sorts of questions like that.

Of course the details of what ANYONE wants to know are based on what they
think is missing in what they already believe.  That's a first-level
statement from PCT.  So what?  If all you are interested in is a succession
of demonstrations that perception is controlled, then you are unlikely to
find much that is interesting to me.  I would like to know where and how,
for example, perceptual signals are derived from multisensory inputs (why
a sound and a sight seem to come from the same object).  The residual
variance proposal was a very peripheral example of that.  I would like
to know whether a multiplier operator is likely to be a common phenomenon
in the hierarchy, or whether we should expect logarithmic compression to
be common.  I'd bet on the latter.

> Since their preconceptions
>about how people work are wrong (because they don't understand the
>consequences of the fact that organisms are locked in a negative feedback
>situation with respect to their environment -- cf. the blind men paper)
>it is only by chance that anything psychologists might want to know about is
>anything more than an illusion from the point of view of PCT.

Some day, I'll write a posting about why conventional psychophysics should
for the most part be valid within PCT, but this isn't the time.

Martin
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