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.

Tuesday, March 1, 2016

Eat Chocolate, Its Good For You...

An advert convincing people to eat more chocolate could be tricky, most people are bombarded day to day with encouragements to eat better and chocolate isn’t normally the first thing you might consider when thinking about being more healthy. To overcome this, I picked a combination of persuasion techniques to do the job. First of all, the advert opens by asking a simple question which most people will answer yes to. I’m encouraging the audience are to make an internal commitment. Research shows that when people make a commitment they are more likely to change their subsequent behaviour to be consistent with it. For example, Sherman (1980), found that asking random participants over the phone to predict what they would say if someone came to the door asking them to volunteer in their neighborhood, to which many people unsurprisingly replied that they would. However a few days later when someone did come to the door, agreement rose by 700 percent. Participants had changed their subsequent behaviour to appear consistent, even though the person that asked them to volunteer supposedly represented a different organisation to that which had initially asked them. This is linked to the theory of cognitive dissonance which states we prefer to have consistent cognition's and behaviors (Festinger, 1957).

Next the advert tell us that ‘Experts Have Found…”, the use of the word expert here is key. Research shows that people are more likely to be persuaded by a message when it comes from a credible source, and a source is seen as more credible if they are seen to be an expert (Hovland and Weiss, 1951). Finally, the advert utilizes the ‘That’s Not All Technique’ when it tells us ‘Convinced Yet? Well Best of All…’. This technique was shown to be effective in research by Burger (1986) who showed that compliance could be increased by appearing to improve the deal. The procedure involved offering a cupcake and two cookies for 75 cents, the control condition, or offering a cupcake for 75 cents then after a short pause offering the two cookies on top, the That’s-Not-All condition. This tactic significantly increased sales. The hope is that upon being made to think that there is even more to the already listed benefits, the audience might be more likely to eat more chocolate.


Burger, J. M. (1986). Increasing compliance by improving the deal: The that's-not-all technique. Journal of Personality and Social Psychology, 51, 277.

Festinger, L. (1957). A Theory of cognitive dissonance. Stanford, CA: Stanford University Press.

Hovland, C. I., & Weiss, W. (1951). The influence of source credibility on communication effectiveness. Public opinion quarterly, 15, 635-650.

Sherman, S. J. (1980). On the self-erasing nature of errors of prediction. Journal of Personality and Social Psychology, 39, 211-221. 

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