THE TWO chronic decorticated dogs whose behavior is discussed in this paper were the last of a series of such preparations which were used in studies on morphine and methadone addiction. The data acquired in the studies on drug addiction have been summarized elsewhere. 1 In the course of these investigations detailed observations on the behavior of these preparations were made, both in the ordinary laboratory environment and in formal conditioned reflex situations. Anatomic studies of the brains of these animals showed that all traces of neocortex had been removed at operation. The data are presented here as a contribution to the problem of the role of the neocortex in acquired adaptations. METHODS Dog 66 was a short-haired black female mongrel about 18 months old, weighing about 9 Kg. Dog 75 was a short-haired white male mongrel of similar age and weight. Both animals had been housed in the animal