[From Bruce Abbott (971230.1100 EST)]
Bill Powers (971230.0308 MST) --
Thought 1. I don't want to build a bridge between PCT and behaviorism. More
Well, that clears the field of action for me, doesn't it?
Thought 2. Some facts discovered by psychologists will probably be
retained, but when PCT principles are applied many of them will look
different. For some reason, I thought of "just-noticeable differences." If
we replicated the experiments that showed this phenomenon, we would still
see it. But if we did a control-system experiment with the same
perceptions, we would not see it. S.S. Stevens actually thought that
perceptions were quantized; a control-system experiment would show that
they are not. Signal-to-noise ratio is not the same thing as perceptions
that occur in discrete steps. This is the sort of thing that would happen,
I believe, with most psychological "facts." When you look at them with
control-system experiments, they will look different.
The idea of the just-noticeable difference originated over 100 years ago
with Fechner, who suggested that there is a threshold below which a given
difference between two stimulus intensities could not be detected. I don't
know what Stevens thought about this idea. Fechner used the JND to
mathematically derive the form of the relation between stimulus intensity
and the experienced intensity of the stimulus (logarithmic). Stevens used a
somewhat different test procedure (magnitude estimation) from Fechner's and
found a power relation rather than a logarithmic one. Neither of these
continuous functions requires the assumption that the underlying perceptions
vary in magnitude discretely.
The standardized hearing test used to assess absolute thresholds for tones
of various frequencies is a simple tracking task. The person being tested
is asked to push a hand-held button until a tone is heard, then release it
until the tone disappears, then press until heard again, and so on. Holding
the button down slowly increases the tone intensity, whereas not holding it
down allows the tone to slowly decrease in intensity. The person ends up
oscillating the tone intensity just above and below the threshold, and the
average is taken to be the threshold for that frequency.
A very different analysis was applied in the early 1960s as an application
of signal detection theory, which was developed at Bell Labs. This analysis
disposes with the notion of threshold. Instead, one derives measures of
"sensitivity" (called D' [D prime]) and "bias." D' is essentially a measure
of signal-to-noise ratio and depends on the signal intensity, noise
intensity, and the observer's sensory capability. Like the individual
control parameters in tracking tasks, it is stable in the individual over
time, except for those changes due to aging or trauma. PCT isn't going to
change any of this.
That statement, if made by somebody with clout, would raise a furor: it
suggests that all psychological facts need to be re-examined, and that if
they were re-examined using the methods of PCT, their status as facts
would, in some unknown array of cases, suffer. Even to say that _some_
facts would change, if somebody of importance were to say this, would imply
that _all_ facts must be re-examined, because we don't know _which_ facts
would change. If the idea that some facts might change were ever accepted,
then psychology would have to be rebuilt from the ground up because nobody
knows now which facts those are. The only way to find out would be to redo
all the basic experiments, but with the possibility of controlled variables
I don't buy these assertions. Control theory makes certain rather definite
statements about what facts ought to be observed if a particular variable is
being controlled. It ought to be rather easy to spot which supposed facts
would change, which would not, and which are simply not spoken to, if PCT
methods were to be applied.
This is why there is absolute resistance to PCT. The moment one admits that
there is a basic phenomenon that has been overlooked by a science, the
entire structure of that science is called into question. The only defense
is to reject PCT, or the idea that it could possibly make any significant
difference to psychology as a science.
It would be more accurate to say that the phenomenon has been
mischaracterized than to say that it has been overlooked. But however you
see it, I don't see how control theory will change the basic empirical facts
of psychology. Perception will still be perception, memory will still be
memory, personality will still be personality. Some explanations will
change, in some areas. For this reason, I do not believe that there is any
"absolute resistance to PCT." Rather, I think that there has been a certain
complacency. Current views seem to be adequate to handle the phenomena and
have served to guide and organize research efforts in a way that has seemed
fruitful. Why change?
Psychooogy is a SYSTEM of thought.
There is no way to change just one thing in a system.
Ah, would that this were so. (I am referring to the first sentence.)
In behaviorism, the reference level cannot be an independent variable. It
must either be a fixed physical property of the organism, or it must
somehow be a function of environmental variables. To allow the reference
level to be an independent variable inside the organism would be to admit
that every behavior is determined in part by the organism and _only_ in
part by its surroundings. And this means that every previous conclusion
that involved expressing behavior as a function of external conditions must
be called into question. A major independent variable has been left out of
consideration, and this independent variable does not correspond to any
observable environmental condition.
Again, I disagree with your chain of reasoning. The only thing behaviorism
asserts is that all conclusions be founded on observables. If you can
measure it, you can admit it. Consider hunger. Presumably hunger is a
function of numerous variables, including the levels of certain nutrients in
the blood, fullness of the stomach, and levels of certain circulating
hormones such as those released by fat cells. At present we don't know all
the factors, or how they combine to produce the hunger being experienced.
However, one _can_ show that an animal's willingness to work for food
increases (up to a point) with the number of hours since last meal, and
decreases in a systematic way with the amount of food ingested. In PCT
these changes in willingness to earn food can be understood via models in
which certain quantities are affected in certain ways by time-since-meal,
amount of food consumed, and many other variables, which result in certain
reference values or perceptual values being produced. But these models to
not "call into question" the observations, they serve to organize and
explain them, in a way different from before.
This omission shows up in subtle forms. One of them is the repeated attempt
by behaviorists to express behavior as a function of reinforcement and
discriminative stimuli. The form of the function that is always proposed is
such that it can be reduced to a single equation, with behavior on one side
of the equation and the environmental conditions on the other. But with the
analysis that takes reference levels and the effect of output on input into
account, we see that _two independent_ equations are always needed, one to
describe the feedback connection and the other to describe the actual
input-output function of the organism. No manipulation of the equations
describing only the observable environment can yield a unique prediction of
_No manipulation of the equations describing only the observable
environment can yield a unique prediction of behavior_. That is the problem
with behaviorism, with its basic philosophy of external determination. That
is the gulf that can't be bridged.
And that is why I don't want to bridge it. To do so would be to attempt to
find common ground for the statements "The observable environment is the
ultimate determinant of behavior" on the one hand, and "The observable
environment is NOT the ultimate determinant of behavior" on the other hand.
The conflict between the PCT view and the behaviorist view is clear and
sharp. There is no way to reconcile not-A with A. And however complicated
the rhetoric gets, that is what the difference between PCT and behaviorism
boils down to: a direct contradiction.
The central assertion of behaviorism is not that the environment causes all
behavior, but that all behavior must be explained in terms of observables.
Until recently, most of the observables have been external to the organism,
i.e., out there in the environment, where they can be measured. This
viewpoint developed at a time when too many "explanations" invoked
unobservable mental events, whose only claim to reality was the very data
they were invented to explain, or invoked "physiological" mechanisms having
the same status. (The practice of invoking hypothetical physiological
mechanisms having no basis in observation came to be called, pejoratively,
"physiologizing.") Presently there are few behaviorists who would insist on
a strictly environmental approach, but all would insist that any
explanations be couched in terms that can be measured, either directly or
indirectly. If PCT were to be rejected by behaviorists, it would not be due
to its specification of references or other aspects of internal
organization. (I say "were to be rejected" because I don't think it has yet
been seriously considered.)
So, Bill, you can make PCT an island if you want to. Be my guest -- lay
under the palms and enjoy the surf. But I've got my bridge-building
construction set right here under my arm, and I intend to use it to connect
PCT with EAB, with or without you.