The trailer above, created by Warner Bros, was used as a trailer for The Conjuring in the US to encourage people at home to go to their nearest cinema and watch this scary movie. Instead of simply showing clips of the film, this trailer includes live audience reactions, as well as several members of the audience reiterating how scary and great the movie was. This is an example of using multiple sources as persuasion.
Harkins and Petty (1981) demonstrated the multiple source effect in Experiment 1. Subjects viewed a videotape of one or three speakers presenting one or three arguments in favour of instituting senior comprehensive exams at their university. After watching the videotape, participants from each condition were asked to fill in an 11 point attitude scale and a series of 4 nine-point semantic differentials (good/bad, foolish/harmful) relating their general feelings towards the arguments posed.
The table above shows that in contrast with any other condition only when participants viewed three speakers with three different (but still all in favour) arguments led to significantly more favourable attitudes towards exams. The three-person-three-argument condition elicited noticeably more favourable attitudes from participants (1.88) than any other condition, the three-person-one-argument scored .30 on average, with the one-person-one-argument scoring the lowest with .03, thus showing the multiple source effect. A similar pattern was found when analysing participants’ positive thoughts, the three-person-three-argument scored the highest with 3.75 and the one-person-one-argument elicited the least favourable attitudes with only 1.50.
Harkins and Petty believed that this difference could not be attributed to the number of sources alone. They believed it was a combination of the increased number of speakers and increased number of similar yet still varying arguments.
In terms of The Conjuring trailer, the multiple sources relaying how great the film was, but with each source having a different argument i.e. “one of the most exhilarating films I have seen in a while”, “scariest movie I have ever seen”, increases the impact of the trailer on people at home. This is because the dissimilar but still favourable accounts help keep the interest and attention of viewers at home, so they listen to more reasons for why they should see this film.
Harkins, S.G, and Petty, R. E (1981a) Effects of source magnification on cognitive effort on attitudes. An information processing view. Journal of Personality and Social Psychology. 40, pp 401-13.
By Kiranjeet Kaur