Roles of instruments in psychological research.

What roles have instruments played in psychology and related disciplines? How have instruments affected the dynamics of psychological research, with what possibilities and limits? What is the psychological instrument? This article provides a conceptual foundation for specific case studies concerning such questions. The discussion begins by challenging widely accepted assumptions about the subject and analyzing the general relations between scientific experimentation and the uses of instruments in psychology. Building on this analysis, a deliberately inclusive definition of what constitutes a psychological instrument is proposed. The discussion then takes up the relation between instrumentation and theories and differentiates in greater detail the roles instruments have had over the course of psychology's history. Finally, the authors offer an approach to evaluating the possibilities and limitations of instruments in psychology.