Induced attack was studied under three conditions: (1) paired experimentally naive rats were exposed to intense electrical shock; (2) experimental subjects, previously trained to respond on a fixed vii ratio of six responses for liquid food reinforcement, were paired with target animals with the reinforcement contingency in effect; (3) experimental subjects were given a history of responding on a fixed ratio of six responses for positive reinforcement in the presence of shock, and finally this group was paired with experimentally naive targets when both the reinforcement and shock variables were present. Pairing experimental animals without shock did not cause attack, nor was bar-pressing behavior appreciably disrupted. Only when electrical shock was imposed upon pairs did attack occur. Furthermore, attack behavior severely reduced operant responding and there appeared to be no recovery of response rates over several sessions.