Interpersonal expectancy effects: the first 345 studies

Abstract The research area of interpersonal expectancy effects originally derived from a general consideration of the effects of experimenters on the results of their research. One of these is the expectancy effect, the tendency for experimenters to obtain results they expect, not simply because they have correctly anticipated nature's response but rather because they have helped to shape that response through their expectations. When behavioral researchers expect certain results from their human (or animal) subjects they appear unwittingly to treat them in such a way as to increase the probability that they will respond as expected. In the first few years of research on this problem of the interpersonal (or interorganism) self-fulfilling prophecy, the “prophet” was always an experimenter and the affected phenomenon was always the behavior of an experimental subject. In more recent years, however, the research has been extended from experimenters to teachers, employers, and therapists whose expectations for their pupils, employees, and patients might also come to serve as interpersonal self-fulfilling prophecies. Our general purpose is to summarize the results of 345 experiments investigating interpersonal expectancy effects. These studies fall into eight broad categories of research: reaction time, inkblot tests, animal learning, laboratory interviews, psychophysical judgments, learning and ability, person perception, and everyday life situations. For the entire sample of studies, as well as for each specific research area, we (1) determine the overall probability that interpersonal expectancy effects do in fact occur, (2) estimate their average magnitude so as to evaluate their substantive and methodological importance, and (3) illustrate some methods that may be useful to others wishing to summarize quantitatively entire bodies of research (a practice that is, happily, on the increase).