This second article of the special section on chaos theory addresses implications of the definition of chaotic behavior for its measurement. The requirements to test the presence of chaotic relations among variables are in agreement with the conceptual and methodological hallmarks of behavioral assessment. (SLD)

This introduction to a special section provides the basic definitions and presents the measurement approaches and data analytic techniques that are collectively referred to as chaos theory. The conceptualization and assessment of unstable behavioral disorders can be strengthened by incorporating elements of chaos theory. (SLD)

A computer-administered version of the Yale-Brown Obsessive-Compulsive Scale was administered to 31 patients with obsessive-compulsive disorder, 16 with other anxiety disorders, and 23 nonpatient controls. The computer version correlated highly with the clinician-administered version and was well understood and liked by subjects. (SLD)