Question about schedules

[From Bill Powers (941118.1440 MST)]

Question about operant conditioning:

If you set up a rat on a FR-1 schedule, what happens if the rat presses
the lever 25 times in a row? Does it get 25 rewards which it can then
consume at leisure?

The reason I ask is that about 30 years ago I got a pair of gerbils and
set them up with a wire lever they could press to get food. They seemed
to get the idea pretty quickly. However, when I looked at them the next
morning all the food was gone from the hopper. I couldn't believe they
had eaten it all (about half a pound), and eventually discovered most of
it hidden under their nest. When they were operating the lever they
didn't really eat the rewards; they stuffed their cheeks full until they
wouldn't hold any more and then dived under the nest to stash it.

Also, putting two gerbils in the same Skinner box didn't work. It caused
terrible fights. When one of them started working the lever, the other
would dash over to the food dispenser and wait. The one at the lever
would quit pressing and rush over to drive the other one away, with much
biting and squealing, then go back to press some more, then dash at the
other one, and so on, apparently, forever. Trying to measure bar-
pressing rates was obviously hopeless.

That was my one and only attempt to do operating conditioning: I
concluded that gerbils are too complex for me to understand.

Anyway, what keeps rats from doing the same thing?



Bill P.

[From Peter Parzer (941118.1000 MET)]

To Bill Powers:

If I understand you right you mean fixed ration 1 with FR1. As far as I
recall this means exactly that the animal is reinforced every time it presses
the lever. The usual setup for such an experiment is that the animal is
only for a short time in the skinner box, maybe 30-60 minutes, depending
on the size of the food pellets. And the foot pellets are so small that
the animal is not able to eat up its daily food allowence during the
experiment. After the experiment the difference of the food eaten during
the experiment and the daily allowance is given freely to the animal in
its cage (not in the skinner box). The daily allowence is usually
calculated that the animal has about 80% of its free feeding weight (that
is the weight when it has as much food as it want without doing anything
for it). As I remember my textbooks, the 80% were choosen because this
is about the weight of animals in freedom.

The setup you mentioned, leaving the animals all the time in the box
with the lever, were used only some years after the experiments of skinner
about the schedules of reinforcement. It was done to study exactly the
behaviors you observed.

Dont take me for an expert of animal experiments. I have never done one
by myself. All this I remember from the textbooks. I hope it still helps.


Peter Parzer
University of Heidelberg
Dept. of Child and Adolescent Psychiatry