Rats' responses on two levers were reinforced according to independent random‐interval 1.5‐min food schedules. In addition, both lever presses were intermittently punished according to several concurrent random‐interval random‐interval shock schedules. For the left, the scheduled rate of punishment was kept constant according to a random‐interval 6‐min schedule. For the right, the rate of punishment varied. As the frequency of punishment for the right lever press increased, its rate decreased. The rate of the left punished lever press increased, however, even though its scheduled reinforcement rate and punishment rate remaine