Effect of Experimenter's Expectancy in Relation to Type and Structure of the Experimental Task

Abstract

The present studies sought to investigate variables related to the mediation of the experimenter's expectancy effect and the generality of this phenomenon. It was hypothesized that the type of experimental task, defined by the presence or absence of factual or emotional components, and the structure of the task, defined by the ambiguity which the subject faces in making the judgments required of him, exert a moderating influence on the transmission of the experimenter's expectancy. Two studies employing a Rosenthal replication and numerosity estimation (Study 1) and a modified Rosenthal replication and modified numerosity estimation (Study 2) were run. 40 male experimenters ran 154 female subjects in both conditions across each of these studies. Subjects rated photographs of faces for success or failure in the Rosenthal replications and the number of dots per stimulus card in the numerosity estimations, with positive and negative expectancies induced in the former and over- and underestimation biases in the latter. It was concluded that the type of task and task-structure are indeed crucial variables for the transmission of the experimenter's expectancy.