[From Rick Marken (920623.1830)]
Well, I got the JASA article --
Nothing to get excited about; the data is the typical
psychology junk -- mostly noise (but what would you expect
from psycho-acousticians (hee hee)).
First, thanks to Bruce Nevin for the info about phonemes. Bruce asks:
Is adaptation a disturbance? (Serious question. I don't understand
what is going on in situations to which people apply this term.)
I call it a disturbance because if affects the perception of the
controlled variable in such a way that action is required to maintain
that variable at a reference level. But it could also be seen as
something that affects the form of the feedback function ,g(o),
that determines how outputs are related to perceptual inputs.
Now, to the Cooper/Nager study.
The basic finding is that adapting to a two syllable word
/repi/ leads to an AVERAGE 6 msec DECREASE in VOT. This is
not a dramatic effect. Ten of the 22 subjects show NO difference
in average VOT or an average INCREASE in VOT. The standard
deviation of VOT measures for each subject is bigger (often
by a factor of 2) than the average difference in each subject's
pre and post adaptation VOT scores.
What this means is that we are dealing with junk data. There
is certainly no evidence of a perceptual variable under control.
To go off and start modelling based on this data (as the
authors do) is simply absurd.
This experiment is a perfect example of the typical psychology
experiment; and it shows why, without understanding control,
much of the existing data in psychology is almost totally useless
to PCT, except by the most remote chance. In this experiment
the authors look at the effect of a stimulus variable (the
adapting stimulus) on an output variable (VOT). My
guess, based on the noisiness of the data (and the highly
variable way that the subjects' output relates to the stimulus)
that VOT is only indirectly related to whatever a subject controls
when speaking the words in the experiment. I have no idea what
might actually be controlled in this experiment. The fact that
there is an average effect of adaptation on VOT suggests that
there is some weak relationship between VOT and a controlled
variable. But this is definitely not the way to go about figuring
out what the controlled variable might be.
The problem is not just the use of adaptation as a "disturbance".
It's that there is no hypothesis about a controlled variable or
measures of the quantitative status of that hypothesized variable.
I can't imagine starting to build a model of speech until I was
able to predict precisely what a person's response would be
to every disturbance to the hypothesized controlled variable.
···
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I just got Martin's post on the VOT study.
(Martin Taylor 920623 21:00)
I've now looked at the Cooper and Nager (1975) article on adaptation of the
perception of Voice Onset Time (VOT). I don't think it is very relevant to
CSG,
I think it does have some relevance. It is a great example of why most
of the existing psychological data is useless for studying control.
This stuff was published in a very prestigious journal. This is the
best that psychology has to offer. Believe me, we pretty much have
to start over.
One problem with the study is that the "adapting" VOT for the (synthetic)
/r@pi/ was 50 msec, and the natural (after /i/) VOT for the subjects' /p/
averaged 57 msec, 7 of the 20 subjects being shorter than 50 msec. So there
wasn't much perceptual adaptation to be expected. And I checked the
individual subject data, which showed no relation between their individual
VOT average and the direction or amount of shift (If their own VOT was being
used as a reference standard that was being affected by the adaptation, one
would expect those with long VOT to reduce, and those with short VOT to
lengthen after adaptation. That didn't happen).
But they said the effect was even bigger in this experiment than
in an earlier study using just syllables for adaptors. I also checked
the individual data -- there was a slight positive relationship
(r = .34) between subkects' own VOT average and the change -- just the
opposite result one would expect if the subjects were controlling
perceived VOT by adjusting VOT.
But one could do an experiment of this kind, usefully, I think.
Do you mean an adaptation experiment or a stimulus/response
experiment like this one. I think what they should have done was measured
potentially controlled variables -- like spectrograms of the
words spoken after adaptation. These could have been compared
to spectrograms of words that were not spoken by the subject
but picked by each subject the best exemplar of the intended word (after
adaptation). At least, that's one possibilty; the idea is to try
to see what remains invariant in the input.
I agree that the study of the controlled variables in speech will
not be easy -- but the approach taken by Cooper/Nager (which
reflects no understanding of the concept of a controlled variable--
and is the approach taken in all psychological experiments in
all fields) is not likely to tell you much -- except that stimuli
have statistical effects on responses. Well, it does tell you that
VOT is probably NOT controlled (though there might be better ways
to tease this out). That IS something -- perhaps enough for JASA
but not enough for the Journal of Living Control Systems
(when it exists).
Regards
Rick
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Richard S. Marken USMail: 10459 Holman Ave
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