Information utility and the multiple source effect

Abstract

In a series of studies, Harkins and Petty (198 la) identified a multiple source eifect whereby information presented by multiple sources received greater scrutiny than did the same information presented by a single source. One implication of this was that when multiple sources presented strong arguments, the arguments elicited more favorable issue-relevant thoughts and more agreement than when the same strong information was presented by a single source. However, when multiple sources presented weak arguments, the arguments elicited more unfavorable issue-relevant thoughts and less agreement than when the same weak information was presented by a single source. This article addresses why multiple sources enhance processing. We report three experiments consistent with the view that multiple sources enhance message processing because of recipients' perceptions that information from multiple sources is more likely to be based on different perspectives and independent pools of knowledge and, thus, is more worthy of diligent consideration. Specifically, in Experiment I we found that the persuasive advantage of multiple sources presenting strong arguments was eliminated when the sources were said to have formed a committee rather than being independent. In Experiment 2, we found that the committee manipulation eliminated the persuasive advantage of multiple sources presenting strong arguments only when this information was available prior to argument exposure and not when it was provided after exposure. In Experiment 3, subjects were led to believe that the multiple sources who formed a committee were either very similar or dissimilar. When the committee was believed to include members with similar perspectives, the persuasive advantage of multiple sources presenting strong arguments was eliminated, but when the committee was believed to include members with dissimilar perspectives, the persuasive advantage of multiple sources was retained. In sum, the present research is consistent with the view that the power of multiple sources to enhance issue-relevant thinking lies in their perceived informational independence and the divergent perspectives they are presumed to represent.