Vocal Emphasis in Experimenters' Instruction Reading as Unintended Determinant of Subjects' Responses

Abstract

Sound motion pictures were made of three male experimenters administering an experiment in person perception to 10 subjects. The task called for subjects to rate the degree of success or failure of people pictured in photographs. An analysis of the experimenters' suprasegmental phonemes and paralanguage from the sound track showed that no subject was exposed to identical vocal emphases of those portions of the instructions listing the subject's response alternatives. All subjects (5) who heard greater emphasis on the rating alternatives associated with success subsequently rated the photos as being of more successful people than the subjects (5) who heard greater emphasis on the failure alternatives (p = 0.004). The correlation between differential vocal emphasis and subjects' subsequent ratings was +0.72 (p < 0.01). The way in which the experimenter reads instructions to subjects, even when instructions are read accurately, can serve as a significant determinant of the subjects' responses to an experimental procedure.