The behaviors of three rats were observed during unsignaled avoidance, conditioned suppression (CS-US), and CS-alone sessions. Behavioral observations, based on 10 response categories, were made in the initial and final sessions of each training condition. A variety of leverpress behaviors characterized an avoidance-trained subject, for example, lever holding, crawling over the lever, pressing with a back paw. By the end of CS-US training, the lever behaviors which typified avoidance training were reduced during the CS, but a different class of lever response had emerged. Moreover, nonlever behavior was increased, for example, locomotions and postural responses. Finally, the frequency of unavoided shocks in CS was elevated over baseline. When the US was removed, the differences in nonlever behaviors between CS and baseline diminished markedly, and an elevated response rate associated with a reduced shock rate appeared during the CS.When signaled response-independent shock (CS-US) is superimposed on avoidance-maintained behavior (Sidman, 1953), shock avoidance in the CS is improved early in CS-DS training. With additional CS-DS pairings, avoidance during CS declines to match that in non-CS periods and then worsens. That is, many more unavoided shocks are received during CS than in baseline (see review by Hurwitz & Roberts , in press).While changes in the criterion measures (e.g., leverpressing, unavoided shocks) have been documented, surprisingly few studies attempt to identify what the subject does during the CS when not engaging in the criterion response. We found only two experiments addressed to this question. Hoffman and Barrett (1971) and Stein, Hoffman, and Stitt (1971) found reductions in food-reinforced responding and other overt activities of pigeons during the CS. A parallel experiment with an avoidance baseline has not been done and was the primary purpose of this experiment.The second purpose arose as we reviewed the literature relevant to the first: Reports on the behaviors of a subject during free operant avoidance training were not found. An exception would be procedures in which two or more subjects are trained simultaneously (cf., Davis , 1969). That is, as avoidance learning progressed, did behavior become more or less stereotypic, or did one form of stereotype replace an earlier form? The present experiment was undertaken to provide information on the behaviors of rats during avoidance and CS-DS training. METHOD SubjectsFour female hooded rats, purchased from Blue Spruce Farms, New York, were used. Subjects were experimentally naive and weighed about 150 g at the beginning of the experiment. ApparatusTwo standard LVE operant chambers (Model 143-20) measuring 31 x 30 x 30 cm (1 x w x d) were used. A 2.5-<:m-wide lever was mounted on the right side of the wall and protruded 2.5 cm into the chamber, 6 cm above the grid floor. A deadweight of 20 g (.2 N) on the lever activated the microswitch. Each chamber was modified to include a houselight in the center of the plastic ceiling and a relay on th...
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