Talking ruler

[From Bruce Abbott (970305.1425 EST)]

Rick Marken (970305.0830 PST) --

Bruce Abbott (970305.0855 EST)

In both proposals the sense of length of the imaginary line is
varied until it matches that of the perceived line. Both
thus function as control systems, bringing the sense of length
evoked by the imaginary line into match with the sense of
length evoked by the perceived line.

Yes. But your description of the control system makes it sound like the
perception (of line length) provides the reference specification for the
judgement. This is precisely what is needed if you want to view the
relationship between perception and judgement of line length in open
loop terms.

The reference is to make the two line-length perceptions the same (implying
the their difference is zero). Of course, the person could choose some
other relationship as reference. If Bill thought that I intended to use one
line-length perception as the reference for the other, he (a) would be
wrong, and (b) could easily have "fixed" the problem without altering my
basic model, simply by offering something like the sentence that begins this
paragraph. Instead, the whole mechanism was rearranged. No, I think the
problem Bill saw lies elsewhere, but I'm not clear what it is.

Still flagellating in the primordial ooze,

Bruce

-from Tracy Harms (970305.1420 PST)

Bruce Abbott (970305.1425 EST)]

Rick Marken (970305.0830 PST) --

Bruce Abbott (970305.0855 EST)

In both proposals the sense of length of the imaginary line is
varied until it matches that of the perceived line. Both
thus function as control systems, bringing the sense of length
evoked by the imaginary line into match with the sense of
length evoked by the perceived line.

Yes. But your description of the control system makes it sound like the
perception (of line length) provides the reference specification for the
judgement. This is precisely what is needed if you want to view the
relationship between perception and judgement of line length in open
loop terms.

The reference is to make the two line-length perceptions the same (implying
the their difference is zero).

The problem is how a person produces an *estimate*, which is a verbal
assertion. Varying an imaginary line until it is perceptually the same as
a seen line, if this can occur at all, does not produce the number which a
"talking ruler" will speak. The hard part -- the adequate association
between "this thingy" and "30 inches", e.g. -- is left unaddressed by
Abbott but solved by Powers: The *proposed numeric length* is varied until
the reaction it provokes fits the important aspect of the thing being
looked at.

These two proposals are vastly different because only one of them includes
any explanation for the generation of the product.

Tracy Bruce Harms
harms@hackvan.com

[From Bruce Abbott (970307.1430 EST)]

Bill Powers (970307.0858 MST) --

If we knew how both the
words and the visual line were converted into perceptions of length, then we
could say that the words are a measure of the perception. But we don't know
that. Just to put it simply, suppose that the line-length were converted to
a sense of length according to the 1.9 power of the actual line length, and
a spoken number were converted to a sense of length according to the 1.4
power of the number. Then we would observe that the spoken word corresponds
to the actual line length according to the 0.5 power of the line length. If
we concluded that the perception of line length went as the 0.5 power of
actual length, we would be wrong. That would be the _apparent_ law, but it
would not be the actual law for either perception. That would be the law
relating the _report_ to the line length, but not the law relating the
_perception_ to the line length.

Yes, I understand your point. However, there are ways around the problem,
although I don't have the time to go into them here. Using his own method,
Norman Anderson (a physicist turned psychologist, would you believe)
concluded that Fechner was right and Stevens was wrong.

This, by the way, is what's wrong with Stevens' Power Law of perception.

Is this problem corrected by Powers' Stevens Law of perception? (:->

Spring break for our campus starts tomorrow and for once I'm actually taking
a vacation, so I'll be out of touch for the next week. (Some say I'm out of
touch when I'm NOT on vacation, so what's the diff?) Do you want me to
appoint someone else to annoy Rick while I'm out, or do you think the vacuum
will fill naturally? Nevermind, I can't leave it to chance. I hereby
appoint Gary Cziko.

Regards,

Bruce

[From Bruce Gregory (970307.1520 EST)]

Bruce Abbott (970307.1430 EST)

Spring break for our campus starts tomorrow and for once I'm actually taking
a vacation, so I'll be out of touch for the next week. (Some say I'm out of
touch when I'm NOT on vacation, so what's the diff?) Do you want me to
appoint someone else to annoy Rick while I'm out, or do you think the vacuum
will fill naturally? Nevermind, I can't leave it to chance. I hereby
appoint Gary Cziko.

I'm hurt that you didn't appoint me, but I think I know why :wink:
Enjoy your vacation!

Bruce Gregory