Psychological tests and measurements (psychometrics) are structured ways of evaluating an individual's inner mental life and external behaviors. They present subjects with more or less standard stimuli to which the subjects respond. Depending on the test, these responses tell us something about their intelligence, abilities and skills, educational and vocational interests and achievements, and personality. Often, the tests are especially helpful in diagnosing organic brain disease—its presence, presumedlocation, and the particular resulting functional deficits. The tests themselves range from structuredquestionnaires or interviews, to pen-and-pencil tasks, to obtaining responses to purposely ill-defined stimuli such as ink blots (Rorschach test). They have been used (1) to evaluate the probability of the presence of a substance-abuse problem, (2) to examine the impact of substance use on behavior and brain function both acutely and chronically, and (3) to assess personality features—profiling which ones are pre-disposed...