[From Rick Marken (951215.0840)]

Bruce Abbott (951214.1635 EST) to Bill Powers (951213.0805 MST) --

Apparently I should not have telegraphed my intentions; you have used the

advance notice to launch a pre-emptive strike designed to nullify virtually

_any_ suggestion I might offer even before I have made it.

Pre-emptive strike? There was no strike at you, Bruce. Bill's on your side.

He, like you and me and the rest of us who understand PCT, is trying to show

that reinforcement theory is the "Ptolomaic" explanation of the phenomenon

called "reinforcement" (behavior and contingent reinforcement rate rise

to an asymptotic value over time); PCT is the far more elegant "Copernican"

explanation of that behavioral phenomenon.

Bill derived the simplest mathematical versions of the two models of the

reinforcemnt phenomenon:

Reinforcement: dB/dt = k1*C - k2*B

PCT: dB/dt = k1*(Co - C)

and pointed out that the solution of the differential equation for the

reinforcement model is an exponential runaway or no behavior at all, neither

of which is actually observed. Bill pointed out that the reinforcement model

could probably be salvaged by making some ad hoc assumptions about rate

limiting processes. Then Bill made a statement to which you seemed to take

considerable offense:

But to look for a "rate-limiting" process is simply to say "Even if the

basic model predicts incorrectly, I choose to defend it."

Perhaps you would find this statement less offensive if you could see that

the addition of "rate-limiting" processes to the reinforcement model is

perfectly comparable to adding epicycles to the Ptolomaic model; it can be

done -- and it might even get the model to work -- but it suggests that

something is fundamentally wrong with the model since there is no independent

basis for making these ad hoc assumptions.

The PCT model, in it's simplest form, explains the basic reinforcement

phenomenon accurately. The PCT model is not perfect yet (just as Copernicus

needed the orbits to be elliptical rather than circular); but continued

experiment comparing both models will (hopefully) show that the PCT model

requires the addition of fewer ad hoc assumptions to keep up with the data

than does the reinforcement model.

This is why we need to do the human operant conditioning experiments. We need

to design experiments that will clearly discriminate the predictions of these

two fundamentally different conceptions of the nature of living systems.

Hopefully, we will be able to do a sequence of experiments that will show

how difficult it is to maintain (via the continual addition of new ad hoc

assumptions) the concept of behavior as controlled or selected by its

consequences (the reinforcement model) and how easy it is to maintain the

concept of behavior as the control of perception (the PCT model).

This is what you want to show, too, isn't it Bruce?

Best

Rick