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)

The Personal Profile System (PPS) is a psychological testing instrument that has been widely used. The construct validity of the PPS was studied through a review of the literature. This paper organizes the literature review into three broad categories: the background of the PPS; the reliability of the PPS; and the validity of the PPS. The PPS is a…