Ralph L. Rosnow

Volunteer subjects and the results of opinion change studies.

Female volunteers and nonvolunteers for a (fictitious) perception experiment participated in a study of opinion change. Opinions about college fraternities were measured before and after the receipt of pro-fraternity, anti-fraternity, or no (control) communication. Volunteers reacted differently from nonvolunteers to pro- and to anti-fraternity communications. In addition, volunteers opinions were significantly less reliable than the opinions of nonvolunteers, i.e., volunteers were more heterogeneous in their opinion-change behavior. The present results taken together with earlier findings raise the possibility that volunteers more than nonvolunteers may more often confirm what they perceive to be Es hypothesis. Therefore, the volunteer status of the subject sample might well be specified routinely in research reports.