Experimenter Behavior as an Unintended Determinant of Experimental Results

Summary

Sound motion pictures were made of 19 Es conducting a person perception experiment with 53 Ss. Ss' task was to rate the degree of success or failure of people pictured in photos. From some of the Ss, Es had been led to expect ratings of success and from some ratings of failure. Actually, Ss were assigned at random to the “success-perceiving” or “failure-perceiving” group, Es showed significant behavioral variation in the way in which they conducted the experiment, Es whose experimental behavior reflected greater interpersonal involvement or warmth obtained ratings of the photos as more successful, Es whose experimental behavior reflected a greater task orientation, greater competence, and a more professional manner obtained ratings significantly more in accordance with their expectancy, regardless of the particular nature of that expectancy.