Conditioned suppression of a positively reinforced shuttle response

Abstract

Rats were trained to run up and down an alleyway for sucrose reinforcement a variable interval schedule. Differential aversive classical conditioning with auditory CSs was then conducted in a separate apparatus (off the baseline) prior to those CSS being presented while the subjects were responding for sucrose in the alleyway. Once the effects of the CSs had extinguished, shock was reintroduced following one CS but not the other (on the differential aversive classical conditioning). Both off the and on the conditioning resulted in conditioned suppression to the CS followed by shock, but little effect of the CS followed by no shock was found. In the on the phase, total suppression of baseline responding occurred at moderate US intensities, and this appeared to result from the subject avoiding the location at which he was last shocked. At lower values, both baseline response rate and relative suppression ratio were functions of US intensity. The results are discussed in relation to the effects found in similar experiments using avoidance baselines. Estes and Skinner (1941) found that food reinforced 1everpressing was suppressed by a conditioned stimulus (CS) that was followed by an unconditioned stimulus (US) of an electric shock. Such conditioned suppression of operant behavior by a preaversive CS has also been found using avoidance baselines (Bryant, 1972). However, Rescorla and Solomon (1967) were able to find support for their motivational account of operant classical interactions from a number of studies carried out in the Pennsylvanian laboratories (e.g., Rescorla & Lolordo, 1965; Rescorla, 1967). In general, these in­ volved training dogs to jump over a hurdle a Sidman