[From Bruce Abbott (951128.1750 EST)]
Bill Powers (951128.0805 MST) --
Me:
Certainly at this stage of the game, reinforcement theory appears
to explain a wide range of phenomena of conditioning better than
PCT does.
BP:
Now, there's a challenging statement. Do you mean that reinforcment
theorists are of the opinion that reinforcement theory explains a wide
range of conditioning phenomena better than PCT does, or are you
asserting that it actually does? A great deal hinges on how you're using
the term "explain." Can you give an example?
I mean that reinforcement theorists are of the opinion that reinforcement
theory explains a wide range of conditioning theory, and that the ability of
PCT to do so remains largely unexplored. There is a sense that
reinforcement theory basically works, and that the anomalous cases will be
found to be consistent with reinforcement theory once the variables at work
are properly understood. People are reluctant to give up a theory that
seems to make sense of a great number of observations in favor of a new view
whose ability to account for at least some of these phenomena has yet to be
demonstrated.
An example: How about autoshaping? Pigeons don't normally peck at
pigeon-keys, so researchers used to have to spend time with each new bird
training it to peck the key using the technique of successive
approximations, otherwise known as response "shaping." Then in 1968, Brown
and Jenkins discovered a procedure that automatically got the pigeons to
peck at the key. The key was illuminated for 20 seconds, and this was
immediately followed by grain reinforcement (no keypecking required). The
keylight then went dark for about 40 seconds. This sequence was then
repeated, over and over. If the pigeon pecked at the key, reinforcement was
delivered immediately. By the end of the session, the pigeon was pecking
happily away and thereby earning its meals. Both the procedure and the
phenomenon were labeled "autoshaping," for "automatic shaping."
The explanation that was eventually developed for autoshaping goes like
this. Hungry pigeons normally exhibit an innate (unlearned) response toward
things that look like they might be edible: they peck at them. Repeated
pairing of key-illumination with grain produces classical conditioning of
this pecking response. The pigeon therefore directs its pecking at the CS
(illuminated key), which has become a kind of substitute stimulus for
eliciting the response. This gets the pigeon pecking at the key. The
keypeck closes the key's electrical circuit to produce immediate grain
reinforcement as in traditional operant conditioning, further strengthening
the response in the presence of the illuminated key, which thus comes to
serve as a discriminative stimulus for operant keypecking (as opposed to the
classically conditioned variety).
It is possible to "pit" the classical and operant effects against one
another. In one study the contingency was arranged such that pecking the
key _prevented_ the reinforcer from being delivered, even at the end of the
20 seconds when it normally would have been given "for free." Again the
pigeons acquired the keypeck response, even though pecking at the key cost
them considerable food. It would appear that the classically-conditioned
keypeck wins over the operantly-conditioned suppression of keypecking, at
least within the parameters tested.
How PCT or HPCT would explain this phenomenon is unclear to me at the
moment, and I'm not asking anyone to come up with one. The point is that
autoshaping can be understood within the framework of what we (think) we
already know about conditioning, without adding any new rules, whereas it is
not clear that the same can be said with respect to the framework provided
by PCT. This is not an argument against PCT, but it does illustrate one
difficulty in getting PCT the attention it deserves within EAB. We're going
to have to start with the kinds of experiments for which fairly simple PCT
models can be developed and tested, as you did for the Verhave avoidance
data, and work up from there.
Regards,
Bruce