| Abstract: | In a signaled-shock situation, the signal's presence serves a warning function (prediction of shock) whereas the signal's absence serves a safety function (prediction of nonshock periods). The relative contribution to preference for signaled shock made by these two potential sources of reinforcement was assessed using a symmetrical changeover procedure in which rats were permitted to control the amount of time spent in one of two mutually exclusive conditions, the signaled and unsignaled states. The stimulus conditions that prevailed in the signaled state differed for several groups of animals. For some groups, the safety function of signals was degraded while the warning function was left intact. For other groups, the warning function was degraded and the safety function was not. The availability of the unaltered feature was then manipulated in both sets of groups to determine its effect on preference for the signaled state. Changeover behavior was strongly related to the availability of the signal's safety function and weakly related to its warning function, indicating that the two variables contribute differentially to preference for signaled shock. Other sources of behavioral control, having little to do with the safety or the warning function of signals, were also demonstrated, suggesting the need for careful control procedures when using changeover behavior as a measure of preference. |
