some hypothetical standard of "normal" behavior. Based on this comparison, we may suspect some form of psychopathology. We may then compare our case against other cases to assess the degree of similarity or difference. This is the process underlying psychological diagnosis. The development of standard diagnostic criteria for categories of mental disorders appearing in the Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (1994, abbreviated as DSM-IV) reflects groupings of many different patients' case histories. Clinicians have noted similarities among patients that permit their problems to be classified into groups. The records of persons previously diagnosed with antisocial personality disorder," for example, have certain important similarities (see Box 3-2)