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.

Monday, February 29, 2016

Eat Your Greens!


Many of you will probably remember being told to "eat your greens" as a child by your parents. However, the media reports that numerous people are not meeting their recommended 5-a-day.

This advert makes use of a few persuasive techniques, including message repetition. According to Zajonc (1968), mere repeated exposure to a message can enhance an individual's attitude towards it, as it appears more believable to them, so they are more accepting of it. Furthermore, Cacioppo and Petty (1979) found 3 to be the optimal number of times to expose a repeated message; any more or any less than this decreased agreeability. Due to these findings, the ad makes use of just 3 repetitive messages:
  • "Eat your greens!"
  • "8 Super Green Foods"
  • "Do you get enough green?"

Automatic activation is another form of persuasion used in the advert. Reading a message with arguments in favour of the focal attitude object ought to increase favourability of other objects related to the focal one (Horcajo, Brinol & Petty, 2010). In this case, the use of the word 'green', and its matching colour scheme, should promote purchase/consumption of fruit and vegetables.

By adding an image of a doctor in the advert, it infers an authorative figure role. This has previously been shown in the well-known study by Milgram (1963), in which participants' continued to obey the orders given by an experimeter wearing a lab coat. Perceived authority thus means a higher rate of agreeability, so the ad makes use of this persuasive technique. As well as this, viewers should see the figure as a credible source and believe the information more readily (Pornpitakpan, 2004)

A final persuasive technique incorporated by this advert is the use of a rhetorical question: "Do you get enough green?". As reported by Petty and Cacioppo (1981), if the message is of low personal relevance to the individual, then they are not naturally processing the statement. Because of this, it enhances their thinking by presenting a new concept to them, especially if there is a strong argument to back it up. In light of this, the ad follows up the question with a few facts on health benefits of eating fruit and vegetables.


Cacioppo, J. T., & Petty, R. E. (1979). Effects of message repetition and position on cognitive response, recall,and persusaion. Journal of Personality and Social Psychology, 37, 97-109.

Horcajo, J., Brinol, P., & Petty, R. E. (2010). Consumer persuasion: Indirect change and implicit balance. Psychology & Marketing, 27, 938-963.

Milgram, S. (1963). Behavioral Study of Obedience. The Journal of Abnormal and Social Psychology, 67, 371-378.

Petty, R. E., & Cacioppo, J. T. (1981). Effects of rhetorical questions on persuasion: A cognitive response analysis. Journal of Personality and Social Psychology, 40, 432-440.

Pornpitakpan, C. (2004). The persuasiveness of source credibility: A critical review of five decades' evidence. Journal of Applied Social Psychology, 34, 243-281.

Zajonc, R. B. (1968). Attitudinal effects of mere exposure. Journal of Personality and Social Psychology, 9, 1-27.

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