Friday, January 19, 2007

This post is about B. F. Skinner's operant conditioning of rats.



B.F. Skinner (1979) studied squirrel and ant behavior before turning more intensively to rats in the later 1930s. His usual rat subject was male, white, healthy, one hundred days old, and a part of an experimental group of the same litter (Skinner, 1938, p. 48). He released them at feeding time into the dark, sound-proof space that came to be called the "Skinner box," even though he said he had never called it a Skinner box (1959, p. 620). He called it an "experimental chamber." Initially unconditioned, they explored the new surroundings as they normally would in nature. Sooner or later, they pressed down on the lever. This caused a pellet of food to drop into a tray. They heard the machine dispense it and they ate it. They would repeat the performance. When he saw a rate of lever pressing that rose above the natural unconditioned baseline level, he concluded that the probability of the lever presses per unit of time had increased. He reported that the behavior had strengthened and concluded that reinforcement had occurred (1938, p. 49).

An "apparatus" called a kymograph tallied action (Skinner, 1938, p. 59). He arranged for each press to cause a pen to nudge up a notch on a sheet of paper that he mounted upon a steadily revolving drum. This machine would draw a total response curve rising gradually with each response and with each bump of the stylus.

The image above in this post represents a total response extinction curve. It shows something akin to the lines he (1938) drew above the actual extinction curves in his rats after he smoothed out the irregularities and fluctuations from the real results. The image in the previous post shows a rate-of-response extinction curve. The previous post explains extinction in more detail. Basically extinction occurs when the researcher stops reinforcing a response he has already conditioned and the rate of response drops very low.

In "Conditioning and Extinction," his third chapter in The Behavior of Organisms, he (1938) included twenty-one graphs of total-response, three graphs of total-response and rate-of-response juxtaposed, one above the other, but no graphs of rate-of-response alone. Skinner could have presented the data either way. Was he in a hurry to publish his findings? Was he punished by the extra work involved in converting the data from the kymographic total-response curves into rates of response? Did the equipment itself condition his behavior? While he modified the behavior of rats, did the rats modify the behavior of B.F. Skinner. I'm only kidding. The evidence of rigor in his work is abundant. I got this joke from a cartoon I once saw.

References

Skinner, B. F. (1938). The behavior of organisms: An experimental analysis (1991 ed.). Cambridge, MA: B.F. Skinner Foundation.

Skinner, B. F. (1959). Cumulative record (1999 definitive ed.). Cambridge, MA: B.F. Skinner Foundation.

Skinner, B. F. (1971). Beyond freedom and dignity. New York: Knopf.

Skinner, B. F. (1979). The shaping of a behaviorist: Part two of an autobiography. New York: Knopf.

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