Expectations of drug effects based on colours and sizes — The importance of learning

Abstract

It has been well known for at least 60 years that the effect of a pill depends not only on its chem-ical-pharmacological (i.e. specific) properties. A considerable proportion of the total effect stems from the so-called placebo or non-specific effects, which seem not to be directly connected to the pharmacological activity of a given drug. As many authors pointed out, the " non-specific " term in itself is a bit confusing: if we define specificity as " specific pharmacological activity " , all other effects are non-specific by definition. On the other hand, these effects can be very specific in terms of the affected body parts or organs or of their direction (e.g. stimulant/sedative) [1]. In the present paper, the term " non-specific " is used as a synonym of placebo. The most often mentioned sources of placebo effects are doctor-patient relationship, the needs and expectations of the patient, suggestions and information given by the doctor, person-ality and psychological state of the doctor and of the patient, the context of treatment, and the perceptual properties of medication [2]. Early researchers of the placebo effect stressed the importance of using tablet colours that simply attract attention (e.g. pink) and are not associated with poisons (like blue or green) [3]. A considerable proportion of the total effect of a drug can be due to non-specific effects. Important sources of such effects are the expectations evoked by the look-and-feel of the curatives. In this study the origin of these expectations was examined. 109 female university students completed two paper-and-pencil tests about expected connections among look-and-feel of curatives and their effects, and about personal drug experiences. Significant pref-erences in perceptual characteristics were found in 10 drug effects out of 19. In 5 cases out of the 10 preferred tablets, the preferences were partly explainable by previous experiences of participants. Although direct learning as a source of tablet colour preferences is an obvious assumption, there has not been any research in this area. Possible consequences of changing drug expectations by direct learning are discussed and several health psychological conclu-sions are drawn.