ABSTRACT
Countless instruments have been used in the science of psychology-in research, for demonstrations and teaching purposes, and in psychological practice. These implements have come to be known as psychological instruments. Before investigating what the term psychological instrument designates, a few remarks on the phrase itself are in order. The term is not often used, and we rarely encounter it even in studies on scientific instruments or on the history of such instruments. Yet the term is not introduced here ad hoc. It has a past of its own.
