Development and preliminary validation of a brief behavioral measure of psychotic propensity

Extensive research demonstrates that the dimensional assessment of psychotic manifestations is a primary strength of the Rorschach inkblot task, which provides an in vivo sample of problem-solving behavior and normative standards concerning the logic and coherence of thought processes and the typicality of perceptual representations. This article presents foundational research for the Thought and Perception Assessment System (TPAS), a Rorschach-based system designed to assess solely for disordered thinking and perceptual aberrations using either the standard 10-card set of inkblots or alternative 3-, 4-, and 5-card short forms. Using data from three patient samples (ns = 61, 93, and 133) and one nonpatient sample (n = 118), we document the equivalence of mean scores across the full and short-form card sets. We also document satisfactory interrater reliability and validity for the full and short forms, as well as strong part-whole reliability coefficients between the short forms and the full form. Consistent with psychometric theory and the principle of aggregation, each type of coefficient decreased as a function of decreasing the number of cards. We discuss implications and future applications in research and clinical assessment.