Work on the instrument that was to become the Minnesota Multiphasic Personality Inventory (MMPI) was begun in 1937 by Stark R. Hathaway, a psychologist, and J. C. McKinley, a neuropsychiatrist. The test authors were stimulated to develop a “personality inventory” based on their pursuit of several objectives. First, they had noticed that a large proportion of patients presenting for medical treatment manifested “one or more complaints that turn out to be psychoneurotic in nature” (McKinley & Hathaway, 1943, p. 161). The two test authors sought to develop an instrument that would be useful in identifying and describing these patients in a manner that was more efficient and effective than the psychiatric interview techniques traditionally used for psychological evaluations of medical patients. Apparently, Hathaway also believed that such an instrument might assist researchers in attempting to evaluate the efficacy of new treatment interventions by allowing for the systematic matching and evaluation of treatment groups. For example, Hathaway (1964), in reference to the use of insulin therapy, which was prevalent in the 1930s, noted:

There was no way that our hospital staff could select a group of patients for the new treatment who would be surely comparable in diagnosis and severity of illness to those from some other setting. It became an obvious possibility that one might devise a personality test which, like intelligence tests, would somehow stabilize the identification of the illness and provide an estimate of its severity. Toward this problem the MMPI research was initiated.