Behaviour Change

PROPAGANDA FOR CHANGE is a project created by the students of Behaviour Change (ps359) and Professor Thomas Hills @thomhills at the Psychology Department of the University of Warwick. This work was supported by funding from Warwick's Institute for Advanced Teaching and Learning.

Wednesday, February 24, 2016

Doctors never lie!

This advert aims to convince the audience to adopt a vegetarian diet by highlighting its health benefits. In addition, it employs a number of persuasive techniques, which may not be noticeable obviously to the audience but can still effectively persuade them to agree to the message of the advert.

Firstly, the advert includes a statement about a negative attribute of the diet by stating it may not be the 'easiest choice' as a dietary option. This is an attempt to create two-sided advertisement, as it then goes on to point out all of the health benefits associated with a vegetarian diet. This technique makes the advert more convincing and limits counterarguments by mentioning a small limitation and then overriding it with a list of advantages. This form of two sided advertisement has been found effective by Bohner, Einwiller, Erb and Siebler (2003), who found that when participants were exposed to two-sided communications, they were more easily persuaded than when they were shown examples of one-sided communications. These results explain how including a two-sided message can make the positive attributes even more salient for the consumer and increases the credibility of the advertisement.

The advert also uses the image of a doctor holding vegetables to promote the vegetarian diet. The use of an expert in health issues is used to make the message more effective, as doctors have a very reliable and trustworthy image. Research in this area has provided evidence that the perceived expertise of the source of information is a highly central persuasion cue, more so than other peripheral cues (Homer & Kahle, 1990). Including the image of a doctor can make the health benefits made in this advert more credible. Evidence for this was shown by Bickman (1974), who found that people were more likely to agree to give a dime to stranger or move away from a bus stop when they were ordered by a man who was in a guard uniform, than when they were ordered to do so by a civilian. A similar effect of attire on compliance was investigated by Bushman (1988), who found uniforms to be both more salient and symbolically significant than ordinary, sloppy clothing.

The use of a doctor in uniform also aims to increase compliance by presenting an authority figure. This is based on the authority principle, which explains that obedience to authority is a common human trait and including someone who was authoritative power can help persuade the audience to agree. Evidence for this comes from the famous electric shock experiments by Milgram (1963), where participants complied to orders asking them to give electric shocks to other participants. Participant compliance occurred because they believed the experimenter (wearing a lab coat) was person with authority; similarly, the use of someone who shows authority in this advert aims to increase agreement for the message in the advertisement.

Lastly, the advert asks the reader to 'Join millions of vegetarians around the world', trying to convince the them that this is socially accepted and welcomed idea. This is an attempt to convey social consensus, more commonly known as the 'bandwagon effect', where the audience is being convinced that a large number of people have adopted the vegetarian diet and encouraged to 'jump on the bandwagon' and become part of this group. Evidence for social consensus as a successful method of persuasion comes from a study by Milgram, Bickman and Berkowitz (1969), who found an important relationship between the size of a crowd and the response of a passerby. In their field experiment, they asked confederates, the 'stimulus crowd', to look up at a random point on a building on a busy street and then observed the behaviour of the passing crowd. They found that as the size of their stimulus crowd increased, so did the number of people who stopped and the number of people who adopted the same behaviour as the stimulus crowd. The same principle has been applied in this advert, which is trying to convey that vegetarianism is a socially accepted lifestyle, currently being adopted by millions of people, which should encourage the reader to try and join these millions by trying the diet.


Bohner, G., Einwiller, S., Erb, H. P., & Siebler, F. (2003). When small means comfortable: Relations between product attributes in two-sided advertising.Journal of Consumer Psychology13, 454-463.

Bickman, L. (1974). The social power of a uniform1. Journal of Applied Social Psychology4, 47-61.

Bushman, B. J. (1988). The Effects of Apparel on Compliance A Field Experiment with a Female Authority Figure. Personality and Social Psychology Bulletin14, 459-467.

Homer, P. M., & Kahle, L. R. (1990). Source expertise, time of source identification, and involvement in persuasion: An elaborative processing perspective. Journal of Advertising19, 30-39.

Milgram, S. (1963). Behavioral study of obedience. The Journal of abnormal and social psychology67, 371.

Milgram, S., Bickman, L., & Berkowitz, L. (1969). Note on the drawing power of crowds of different size. Journal of Personality and Social Psychology, 13, 79 - 82.

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