~EnAVIOn TaEaAVY (1973) 4, 137--140 Behavioristic Approach to Multiple Personality: A Case Study ROBERT J. KOHLENBERG t University of Washington Multiple personality in a 51-year-old resident of a mental hospital was observed and classified into three behavioral repertoires. After baseline rates had been established, one of the repertoires was reinforced and then ex- tinguished. Rate of occurrence of the personalitie3 was found to vary with reinforcement contingency. Naturally occurring contingencies were dis- cussed in relationship to the etiology and maintenance of multiple person- ality behavior in a hospital ward. Most of the classical psychopathologic disorders have been subjected to attempts at analysis and study from behavioristic standpoint. Perhaps due to its relative rarity (Taylor & Martin, 1944), multiple personality has not been discussed or studied from a learning basis. This paper describes the behavioral analysis and treatment of a patient who ex- hibited a multiple personality. Two important properties of this patient's behavior lead to the con- clusion that the patient had a multiple personality. First, a large number of the verbal and nonverbal behaviors of the patient could be reliably classified as belonging to one of three distinct repertoires. Second, any one of the three repertoires would occur from time to time even though there was no apparent change in external stimulus conditions. This last property is essential to the definition of multiple personality since dis- tinct repertoires could probably be identified in everyone, but the occurrences of such repertoires are related to apparent changes in the stimulus conditions. METHOD Subject The subject was a 51-year-old male who had been a resident of a large state mental hospital since he was 35 years old. At the time of admission he was diagnosed as a schizopiarenic reaction with multiple personality. The multiple personality con- 1Requests for reprints should be addressed to Robert J. Kohlenberg, Psychological Clinic, University of Washington, Seattle, WA 98105. 137 Copyright © 1973 by Academic Press, Inc. All rights of reproduction in any form reserved.