Some Experimental Observations on Gastro intestinal Lesions in Behaviorally Conditioned Monkeys

&NA; Eleven of 19 monkeys used in chronic psychological‐conditioning experiments developed gastrointestinal disease. Although the program for each animal was different, for the most part experiments were directed toward a study of emotional behavior. Among the lesions found were gastric hemorrhage and erosion, duodenal ulceration, enteric intussusception, and chronic colitis. In a controlled study of a single behavioral procedure (avoidance behavior), 2 experimental monkeys developed duodenal ulceration while the 2 control animals showed no abnormality. The possible etiologic factors responsible for this occurrence and their significance from the standpoint of investigating the pathogenesis of “psychosomatic” disease have been discussed.