Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Michael Perone.


In operant conditioning experiments concerned with punishment, when electric shock is contingent on an animal's response, response rates typically decrease. In some cases, however, response rates increase. Four experiments investigated these paradoxical effects of shock by manipulating shock intensity and the time between two consecutive responses (interresponse time) that produces shock. Lever pressing by rats was maintained by a variable-interval 40-s schedule of food reinforcement. Shock followed either relatively long (Experiments 1 and 2) or relatively short (Experiments 3 and 4) interresponse times. The range of interresponse times eligible for shock was raised by lowering or raising the interresponse times that produced shock. Shock intensity was raised from 0.05 mA to either 0.4 mA or 0.8mA. Shock contingent on long interresponse times punished long interresponse times, leading to increased response rates. Shock contingent on short interresponse times punished short interresponse times, leading to decreased response rates. In two experiments, raising the range of interresponse times that produced shock increased or decreased response rates depending on whether the interresponse times were long or short, respectively. In the other two experiments, there was an effect of shock intensity. When long interresponse times produced shock, low intensities punished long interresponse times and increased response rates. High intensities had the opposite effect. When short interresponse times produced shock, high shock intensities punished short interresponse times and decreased response rates more than low intensities. These results demonstrate that interresponse times may serve as functional units of behavior when the behavioral consequence is a punisher and may explain why punishment procedures occasionally increase responding. Moreover, they establish experimental parameters that may be useful for future studies of punishment.