More than a dozen pencil-and-paper questionnaires or scales have been developed in an attempt to measure the interrelated constructs of schizotypy, the predisposition to schizophrenia or to psychosis, and schizotypal personality disorder. The attraction of this research is its potential for major payoff should it be completely successful. If researchers could use measures of traits and symptoms to identify schizophrenia-prone persons in advance of clinical decompensation, they would have a powerful tool for studying many of the important questions about schizophrenia. They could better seek the events that precipitate the disorder in predisposed persons or, conversely, identify protective factors that help prevent decompensation. They could study the biological substrate of the predisposition before the disruptive intrusion of the psychotic episode and the side effects of treatment. Geneticists could determine the mode of genetic transmission of the predisposition to schizophrenia and determine whether some schizophrenia-prone persons carry a genetic predisposition whereas others do not. Clinicians could attempt prophylactic intervention in advance of the disaster of the schizophrenic episode.

We review these scales together with some evidence for the validity of each, giving most detailed attention to five scales developed in our own laboratory. Our review is, of necessity, a very selective one. The majority of the numerous publications on these scales are not covered. In particular, our discussion of the validity of the scales focuses on the evidence provided by interviews for schizotypal and psychotic-like symptoms in high-scoring persons on the scales. We do not examine the large literature of laboratory studies of deviant scorers. The laboratory studies mainly test hypotheses about poor performance on tasks on which schizophrenics perform badly.