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.

Thursday, February 4, 2016

Trust Me, I'm a Doctor.

This is the advertisement of a toothpaste brand called Sensodyne. I was impressed by the way it advertised when I first watched it several years ago. Unlike adverts of other toothpaste brands, which either show animation of a tooth and oral bacteria or the super white teeth that the celebrity has got, Sensodyne would like to invite a “dentist” whom will be interviewed in the advert to simply talk about teeth cleaning and introduce the brand. Instead of vivid images in the advertisement, the magic weapon for Sensodyne is none other than the “dentist”, that is, the lady in hospital white who professionally and formally says “I recommend Sensodyne to my patients.”

It is the “dentist” who makes the advert as well as the product highly persuasive for consumers. And the persuasive technique applied here is Authority, which refers to the principle that people are voluntarily deferential to those in positions of power. In this case, authority is revealed through distinctive symbols, such as the lady’s identity as a dentist, the title (i.e., Dr.), and the clothes. Authority figures are usually more likely to gain compliance because of the high persuasiveness and trustworthiness. More specifically, people would like to go along with those with special knowledge and impressive credentials in a certain field (e.g., doctors; lawyers; professors). It’s worth noticing that people not only believe those with actual power to whom we follow, but are also inclined to comply with anyone “appearing” to be authoritative. In the advertisement, even though we can’t tell with confidence that the lady is a real dentist, how she looks and what she says may convince us to some extent her credibility.

The effect of authority upon persuasion is empirically indicated in the study of Harvey and Hays (1972). The study aimed to investigate whether people with different levels of dogmatism would be influenced differentially by communications from sources of high or low authority. One prediction being made is that the higher the authority goes, the greater the persuasion towards people especially those high-dogmatic (according to the theory of dogmatism; Rokeach, 1960).

In the experiment, eighty high- and low- dogmatic subjects were recruited and were told to read a speech which the speaker advocated stringent governmental control of industrial air pollution in a highly opinionated tone. Ss in the high-authority condition were informed that the speech was given by a research physiologist; those in the low-authority condition were told that the speaker was a high school student. After reading the speech, each subject was asked to rate the speaker on an impression scale, to complete a memory questionnaire measuring how well the subject could recall the speech, and lastly answer a set of questions concerning with their personal attitude about governmental control of air pollution.

Table 1 shows the means for the agreement with the speaker’s position for both high-authority and low-authority conditions. As can be seen, subjects who were presented with the high-authority communication gave more agreement with the speaker’s position, and no matter they were high-dogmatic or low. It can also be noted from Table 1 that high-dogmatic subjects were more likely to be persuaded by a high-authority communication than by a low-authority one, while low-dogmatic subjects given either high- or low-authority source were influenced similarly. The results are consistent with the prediction.

Why does authority persuade and influence on us? Well it could be explained from our past experiences. We were surrounded by older, smarter, and more experienced people (e.g., parents; teachers) when as a child, who always taught us what we should do. And we would be punished for disobedience. In fact, our compliance with authority arises spontaneously rather than by force, and we even reply on it. One explanation is that persuasion of authority can usually be beneficial. Imagine, how could we survive well without the guidance and protection provided by all those authority figures?


Harvey, J. & Hays, D. (1972). Effect of dogmatism and authority of the source of communication upon persuasion. Psychological Reports, 30, 119-122.
Rokeach, M. (1960). The Open and Closed Mind. New York: Basic Books.

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