Aversive shocks are known to produce aggression when the shocks are not dependent on behavior and to suppress behavior when the shocks are arranged as a dependent punisher. These two processes were studied by presenting non-dependent shock to monkeys at regular intervals, thereby producing biting attacks on a pneumatic tube. Immediate shock punishment was simultaneously delivered for each biting attack. The attacks were found to decrease as a function of increasing punishment intensity. These results show that aggression is eliminated by direct punishment of the aggression even when the stimulus that is used as a punisher otherwise causes the aggression.Aversive shock changes behavior in a direction that is determined by the temporal relation of the shock to the behavior. If the response terminates shock, the rate of that response increases and the process is called escape (see recent review by Dinsmoor, 1968). If the response produces the shock, the rate of that response decreases and the process is called punishment (see review by Church, 1963;Solomon, 1964;Azrin and Holz, 1966).In addition to these operant effects, shock also has eliciting effects. Shocks that are received by an animal independently of behavior will produce attack against other animals or objects (Ulrich and Azrin, 1962; Azrin, Hutchinson, and Azrin, Hutchinson, and Sallery, 1964(a); Azrin, Ulrich, Hutchinson, and Norman, 1964b; and see recent review by Azrin, 1967). The existence of this "painelicited" attack raises important theoretical and applied questions as to whether the usual operant effects of shock will occur if the response being punished is an attack response rather than a response that is not directly elicited by shock. Since shock elicits attack, the use of shock as a punisher might well increase the attacks rather than decrease them, a possibility that has been further considered