FROM THE DESK OF THE GUEST EDITORS Evolution of a Theory: HowMeasurement Has Shaped Ayres Sensory Integration

Scientific theory evolves through phases. Scientists observe phenomena, classify their observations, examine and explain causation, and attempt to understand their results in varied circumstances. If anomalies are found that do not mesh with the theory, revision occurs, and the theory is improved (Christensen, Carlile, & Sundahl, 2001). Each stage requires accurate and precise measurement and, therefore, appropriate measurement tools. The body of scientific inquiry developed byA. JeanAyres is deeply rooted in systematic and methodical measurement, and her work marked the first effort by an occupational therapist to build a theory for clinical application with an evidence-based approach. The trajectory of the growth of Ayres Sensory Integration (ASI), beginning in the 1950s with continual advancements from the ongoing contributions of the researchers who have built on her seminal work since that time, has occurred simultaneously with the widespread use of more rigorous research methods, attention to measurement of fidelity, greater usage of exploratory and factor analysis, and more routine practice of examining multivariate research problems with computer statistical programs (Century, Rudnick, & Freeman, 2010; Elmore & Woehlke, 1988; Keselman et al., 1998; Ottenbacher & Peterson, 1985; Press, 2013; Tukey, 1980; West, Carmody, & Stallings, 1983). This special issue of the American Journal of Occupational Therapy consists of an impressive compilation of the widereaching application of the concepts that have evolved from those early efforts in measurement and that now continue to serve as a model for the profession, in line with the American Occupational Therapy Association’s (2007) Centennial Vision aiming toward “a powerful, widely recognized, science-driven, and evidence-based profession” (p. 613). This issue provides multiple examples of the improvements in methodological rigor that occupational scientists have brought to the study of ASI theory. The articles includemeasurement in sensory integration across age spans and diagnostic categories, with implications for theory and practice ranging fromassessment to intervention. In “The Issue Is” article by Schaaf et al. (2014), the current state of measurement in sensory integration is thoughtfully analyzed and articulated. In this editorial, we highlight the ways in which the foundations in measurement established by Ayres have evolved and how this earlier work connects with current and future trends.