HISTORICALLY, the concepts of the placebo and the placebo effect have been quite broad; only in recent decades have they been narrowed to become virtually synonymous with the administration of inert medications. Especially in the last three decades many investigators have sought to define the conditions under which the placebo effect operates; and several have sought to define the personality characteristics of persons prone to show the placebo effect. In this paper, we shall state some hypotheses which derive from their findings, and report an experiment in which they are tested.
For our experiment we shall use the historically broad definition of the placebo effect, stated by Shapiro to include the following:
Any therapeutic procedure (or component of any therapeutic procedure) which is given (1) deliberately to have an effect or (2) unknowingly and has an effect on a symptom, syndrome, disease,
Campbell JH, Rosenbaum CP. Placebo Effect and Symptom Relief in Psychotherapy. Arch Gen Psychiatry. 1967;16(3):364-368. doi:10.1001/archpsyc.1967.01730210104016