[From Bruce Abbott (950606.1400 EST)]
Bill Powers (950606.0000 MDT) --
Bruce Abbott (950605.1210 EST)
The observed increase in responding is _by definition_
reinforcement.
But notice that if you artificially elevate the rate of delivery of
food-pellets, the most likely effect is a _reduction_ in the rat's rate
of lever-pressing, because (going the rest of the way around the loop),
the change in food delivery rate is opposed by the change in the
behavior rate. This assumes, of course, that the system is inside the
normal control range, and not at an extreme of deprivation where the
relationships reverse.
You have still never explicitly commented on this problem: that you get
the assumed relationship between increases of behavior and increases in
reinforcement only for the most extreme degrees of deprivation. Is this
something that behaviorists have simply agreed to keep quiet about? Some
of them certainly haven't agreed to this.
I believe that you have drawn an incorrect conclusion from one graph showing
what happens to asymptoticly maintained response rates as the ratio
requirement of a ratio schedule is varied. Perhaps a clearer picture might
emerge from examining data on runway performance. Rats are food-deprived to
some criterion and then trained to run from a start box, down a
straight-alley, and into a goal box which contains a certain amount of
standard laboratory rat chow. What is measured is the speed of running.
Running speed will vary directly with (a) the amount of food provided in the
goal box and (b) the level of deprivation (so long as the level is not so
high as to begin to incapacitate the rat).
The rats are run for only one or at most only a few trials per day so as to
prevent much of a satiation effect. Both of the manipulations (deprivation
and amount of food) may be viewed as affecting the attractiveness of the
goal. For a rat not AT the goal, the experienced error for not being at the
goal will be proportional to the goal attractiveness. Larger errors will
lead to greater output (faster running).
In this description I have oversimplified, especially as there are multiple
control systems at work governing perceptions at several levels and I have
improperly collapsed these into one, but I think I've communicated the basic
idea: larger reward would be expected to produce faster running if you
properly analyze the situation from a control-system perspective (remember,
each visit to the goal box is having little or no effect on the error in the
upper-level nutritional control system even with relatively large reward;
the experimental procedure essentially opens the loop on this system).
An equivalent manipulation to changing the ratio would be to increase the
distance the rat has to run to reach the goal. Now it must run for a longer
time and use more energy to reach its perceptual reference state of being in
the goal box, eating the food. If the trip is not too taxing the extra
effort may have little effect on running speed, and experimenter will have
gotten more distance out of the rat for the same reward. The curve will
begin to reverse only when the effort expended begins to seriously detract
from the attractiveness of the goal. If the analysis takes into account the
"reinforcement" received at the goal AND the "punishment" received in terms
of fatigue, the results appear to be quite compatible with a reinforcement
analysis rather than something that one needs to "keep quiet about."
Staddon certainly didn't see anything problematic. And these results have
absolutely nothing to do with operating at the extreme end of the
deprivation scale. The rat's control system is operating within its normal
range, but a key component of that (hierarchical) system is operating with
its feedback loop open. Larger errors lead to larger output, until error in
another control system (fatigue) begins to have an increasingly large
opposite effect on the output.
I realize that in the above description I have not done full justice to
either the reinforcement or PCT analysis of the experimental results as I
have not yet had a chance to think the problem through in detail, but I do
believe I have captured at least the essence of the explanation.
Regards,
Bruce