IT HAS been suggested that the "rigidity"shown by the Einstellung method, as exemplified hi Luchins' (11,12,13,14) water-jar problems, is a "general response characteristic that pervades all aspects of an individual's behavior" (3, p. 165). If this were so, a person who behaves rigidly when trying to solve water-jar problems should also behave rigidly when trying to solve other types of problems, and thus his adjustment to his environment would be affected. Rigid and nonrigid people should differ, then, in the kind of personality traits they develop. Rigidity, defined as the resistance of the Einstellung (set to respond in a given way) to change when a more adequate answer can be given than the one brought about by the Einstellung, was studied in the present experiment by means of a test of similarities of words, in order to investigate rigidity hi solving problems of a verbal, rather than numerical, nature. Ten personality traits, general activity, restraint, ascendance, sociability, emotional stability, objectivity, friendliness, thoughtfulness, personal relations, and masculinity, were studied by means of the Guilford-Zimmerman Temperament Survey, a standardized personality test (6).Results from previous studies have not given a clear-cut answer to the problem of the generality of rigidity. In the first place, varying, even contradictory, concepts, such as fixation of response (5), lack of variability (15), perseveration (1, 2), degree of impermeability of boundaries (8, 9, 10), as well as Einstellung, have been equated with rigidity. Some individuals working hi this area, for example, Goldstein (5), Werner (20,21), and Cattell and Tiner (2), also distinguish more than one kind of rigidity.In general, the various definitions of rigidity seem to be of two types, those that conceive of rigidity as evidenced by repetition within one. situation (1,12,14,16) and those that consider it to be a basic trait underlying many or all kinds of behavior (3,9,15,17). As a