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The Experimental Analysis of Behavior

The 1957 American Scientist article, reproduced in full

B. F. Skinner


So far our data have been taken from the pleasanter side of life—from behavior which produces positive consequences. There are important consequences of another sort. Much of what we do during the day is done not because of the positive reinforcements we receive but because of aversive consequences we avoid. The whole field of escape, avoidance, and punishment is an extensive one, but order is slowly being brought into it. An important contribution has been the research of Murray Sidman [10] on avoidance behavior. In the Sidman technique, a rat is placed in a box the floor of which is an electric grid through which the rat can be shocked. The pattern of polarity of the bars of the grid is changed several times per second so that the rat cannot find bars of the same sign to avoid the shock. In a typical experiment a shock occurs every 20 seconds unless the rat presses the lever, but such a response postpones the shock for a full 20 seconds. These circumstances induce a rat to respond steadily to the lever, the only reinforcement being the postponement of shock. The rat must occasionally receive a shock—that is, it must allow 20 seconds to pass without a response—if the behavior is to remain in strength. By varying the intervals between shocks, the time of postponement, and various kinds of warning stimuli, Sidman has revealed some of the important properties of this all-too-common form of behavior.

2012-01SkinnerF11.jpgClick to Enlarge ImageA sample of behavior which W. H. Morse and the writer obtained with the Sidman procedure is shown in Figure 11. Here both the interval between shocks and the postponement time were 8 seconds. (White space has been cut out of the record and the separate segments brought together to facilitate reproduction.) The records report a 7-hour experimental session during which about 14,000 responses were emitted. Occasional shocks are indicated by the downward movements of the pen (not to be confused with the fragments of the reset line). A significant feature of the performance is the warm-up at a. When first put into the apparatus the rat “takes” a number of shocks before entering upon the typical avoidance pattern. This occurs whenever a new session is begun. It may indicate that an emotional condition is required for successful avoidance behavior. The condition disappears between sessions and must be reinstated. The figure shows considerable variation in over-all rate and many local irregularities. At times small groups of shocks are taken, suggesting a return to the warm-up condition.

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