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, January 27, 2015

To be fat or not to be fat? The choice is simple.

"Change4Life" is a government-funded NHS campaign aimed at improving the health (and waistlines) of the nation by promoting the positive benefits of exercise and good diet.  The TV advert above focuses on Alfie, who essentially has just two options - stay unhealthy with an unsightly tyre-shaped middle which negatively impacts all areas of his life (including sex!) OR get healthy by following a few simple steps (eat less, move more).  And when you put it like that it seems pretty obvious what Alfie should choose do.

This persuasive technique is known as the "least-of-evils" tactic.  By limiting the number of choices available to the audience and only providing them with an attractive option (i.e. get healthy with a few simple steps) and a stinker of an option (i.e. stay fat and not be able to climb the stairs or have sex), the audience will be induced to select the former option as compared to the negative outcomes of the second option it is by far the lesser of two evils - even if it does require some self-motivation and restraint!

This technique was demonstrated by Vidmar (1972) in his simulated jury experiment.  Mock jurors were asked to read a transcript of a murder trail (which contained only neutral information) and then asked to return a decision upon the defendant's guilt and what punishment he should receive.  However, the number and the severity of the decision alternative the jurors could choose from were varied as follows: (1) guilty of first degree murder OR not guilty; (2) guilty of second degree murder OR not guilty; (3) guilty of manslaughter OR not guilty; (4) guilty of first degree murder OR second degree murder OR not guilty; (5) guilty of first degree murder OR manslaughter OR not guilty; (6) guilty of second degree murder OR manslaughter OR not guilty; (7) guilty of first degree murder OR second degree murder OR manslaughter OR not guilty.  As seen in the table below, it was found that jurors were more likely to decide on a guilty verdict (i.e. a lesser number of participants concluded ‘not guilty’) when the potential penalty options contained at least one moderate penalty which had less severe consequences for the defendant (likely to get a shorter prison sentence for second degree murder or manslaughter than for first degree murder).

First degree


Second degree





Not guilty
Table 1. mock jurors verdict decision as varied per the options provided.

This experiment clearly demonstrates the "least-of-evils" effect because when the options are limited (i.e. can only choose first degree murder or not guilty) and one option appears unnecessarily harsh (i.e. first degree murder), a person feels obliged to choose the other option even if it is not ideal either (i.e. not guilty verdict).  The use of this technique can be clearly seen in the "Change4Life" advert as the viewer is only being provided with two options that represent vastly different outcomes of which only one is positive.  Applied more broadly, the “least-of-evils” technique would suggest that it you really want to persuade someone to do something you should pretend to give them two options, but make the alternative so undesirable that really they have no choice but choose the other option – the one you wanted them to choose all along anyway!

Vidmar, N. (1972). Effect of decision alternatives on the verdicts and social perceptions of simulated jurors. Journal of Personality and Social Psychology, 22, 211-218.

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