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, March 2, 2016

Isn't it time you started living longer? Health benefits of the Mediterranean diet

The above advert promotes the health benefits of adhering to the Mediterranean diet. In order to persuade viewers of the health benefits of this diet choice, the advert utilises several persuasive techniques.

Firstly, the title uses a rhetorical question, as rhetorical questions have been shown to lead to more favourable attitudes towards a persuasive message when strong arguments are presented (Burnkrant & Howard, 1984).

The rhetorical question at the start of the advert also uses social consensus as a persuasive technique. Research has found that being shown that a large number of other people are performing a behaviour results in increased compliance when requested to perform that behaviour, as it provides social proof of what is the “correct” thing to do (Reingen, 1982). The statement “millions are living longer than you” utilises this technique by highlighting the high number of long-lived populations who have benefited from this diet choice. This use of social consensus aims to use the large number of long-lived populations adhering to the Mediterranean diet (or similar diets) to strengthen the argument that such a diet is the “correct” choice in terms of health outcomes, etc.

Another key persuasive technique used in the advert is a fear appeal. Persuasive messages containing appeals to negative emotions such as fear have been shown to be highly effective, particularly when such messages include recommendations for avoiding the fearful consequence (Maddux & Rogers, 1983; Pratkanis, 2007). The advert uses this technique by comparing the two “choices” of either following this diet choice or contracting heart disease and various other serious conditions. Combined with a fairly graphic image of the physiology of a heart attack, this fear appeal aims to instil a strong emotional reaction in the audience, and also offers (dietary) recommendations for how viewers can avoid these fear-inducing outcomes.

The advert acknowledges that “A diet full of fast food, red meat and saturated fat might seem like the easy option”, which is then countered by reiterating the serious health implications, given which the audience “can’t afford NOT to make the switch”. In doing so, the advert makes use of the “defusing objections technique”, in which the audience’s likely objections to a persuasive message are refuted before they are even raised: This technique has been shown to increase the persuasiveness of messages in areas such as climate change (Pardini & Katzev, 1986). The advert identifies one of the audience’s possible objections to the message (processed, fattening foods are perhaps easier to prepare), and then refutes this possible objection – in the long-term, extremely poor health and reduced life expectancy hardly seems like an “easier” option.

By stating “Mortality or Longevity: You are free to make your choice”, the advert utilises the “but you are free to… technique” (Pratkanis, 2007). Research has shown that when individuals are made aware that they are free to “say no” or choose freely between several options, this can increase the effectiveness of the message in changing behaviour (Guéguen & Pascual, 2000). It is made clear to viewers of the advert that they are free to choose between the dietary choices presented, which should increase the persuasiveness of the message according to the above-cited research. The bottom statement also aims to strengthen the aforementioned use of fear appeal. Additionally, the statement (as well as the advert in general) employs the perceptual contrast principle (Cialdini, 2007), according to which people make judgements based on relative, not absolute quantities. The advert makes use of this principle by contrasting the health benefits of the Mediterranean diet with the negative consequences of following a diet high in saturated fats, etc., and thereby aims to make the health benefits of the MD appear greater in contrast to developing the list of diseases the diet could be used to prevent.

Finally, the advert in general uses information from experts (medical journals), as persuasive messages have been shown to be more effective when coming from a credible source (Hovland & Weiss, 1951), and it also makes use of multiple arguments to convince viewers of the Mediterranean diet’s health benefits (prevents heart disease, cancer, diabetes, premature mortality, etc.), as presenting a greater number of arguments has also been shown to increase the effectiveness of a persuasive message (Petty & Cacioppo, 1984).


Burnkrant, R. E., & Howard, D. J. (1984). Effects of the use of introductory rhetorical questions versus statements on information processing. Journal of Personality and Social Psychology, 47(6), 1218-1230.

Cialdini, R. B. (2007). Influence: The psychology of persuasion. New York: Collins.

Guéguen N. and Pascual A. (2000), Evocation of freedom and compliance: The "But you are free of…" technique, Current Research in Social Psychology, 5, 264-270.
Hovland, C. I., & Weiss, W. (1951). The influence of source credibility on communication effectiveness. Public Opinion Quarterly, 15, 635-650. 

Maddux, J. E., & Rogers, R. W. (1983). Protection motivation and self-efficacy: A revised theory of fear appeals and attitude change. Journal of Experimental Social Psychology, 19(5), 469-479.

Pardini, A. U., & Katzev, R. D. (1986). Applying full-cycle social psychology to consumer marketing: The defusing objections technique. Journal of Economic Psychology, 7(1), 87-94.

Petty, R. E., & Cacioppo, J. T. (1984). The effects of involvement on responses to argument quantity and quality: Central and peripheral routes to persuasion. Journal of Personality and Social Psychology, 46(1), 69-81. 

Pratkanis, A. R. (Ed.). (2007). The science of social influence: Advances and future progress. Psychology Press. 

Reingen, P. H. (1982). Test of a list procedure for inducing compliance with a request to donate money. Journal of Applied Psychology, 67(1), 110-118. 

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