You want to be more persuasive, don't you?

Robinson's latest advertising campaign takes advantage of a well-known health recommendation that we should all drink eight glasses of water a day, and that some of us don’t actually manage to do that. The leading squash provider has splashed the following on billboards, Twitter, YouTube and other modes of communication: 

“Enjoy drinking more water” by adding a drop of Robinson’s Squash to your glass, improving the taste and contributing to your 5 a day with “real fruit in every drop.” What more could you want from Robinson’s squash?!

If that wasn’t enough to persuade you to buy their squash, they use a rhetorical question as seen below, which accompanies their adverts:

The rhetorical question used here forces the audience to think more carefully about the message they are being posed with. In this case, losing a glass of water a day through an automatic process like breathing forces you to think about how you should replenish that glass of water. If you don’t usually drink enough water a day, chances are you perhaps don’t get time or don’t like the plain taste. So, Robinson’s are telling you to enjoy the taste of water, thus drinking more of it, by enhancing it with their squash.

A classic study investigating the persuasive effect of rhetorical questions generating powerful arguments comes from Zillmann (1972), who used rhetorical questions to alter participants’ recommended prison sentence terms. A between-subjects 2 (grammatical form: statement or rhetorical agreement question) x 3 (levels of initial attitude: unfavourable, neutral, favourable) factorial design was used to investigate the effect of rhetorical questions on persuasion. 

Participants were randomly assigned to conditions and their level of initial attitude was manipulated by giving them background information towards the desired level of initial attitude. To ensure they had this attitude in mind, they were required to rate their attitude on a scale of 1 to 7. The “trial” they were recommending a sentence on involved a teenager who was charged with second-degree murder of his father. The defense claimed that the killing was manslaughter. 

Once they had rated their attitudes, they listened to a summary of the defense’s argument. This either took the form of statement such as “Johnny was a peaceful boy”, or rhetorical agreement question such as “Johnny was a peaceful boy, wasn't he?”

Table 4 shows the recommended prison terms given by participants. Participants gave lower prison sentences in the rhetorical agreement question condition across all levels of initial attitudes. This demonstrates how powerful messages with rhetorical questions can be, especially when trying to persuade. 

The effect was explained by Zillmann as a result of operant conditioning. Typically, when using a rhetorical question, the audience of the message pays more attention to the content of the message and so it needs to be strong. As such, people usually only use rhetorical questions if their argument is strong, meaning that over time we are used to strong arguments where a rhetorical question is used. Therefore, when posed with a rhetorical question we expect the message to be strong (even if it is not).

So, Robinsons are taking advantage of a health recommendation by framing it in a rhetorical question... Better start drinking more water (with squash)!

References
Zillmann, D. (1972). Rhetorical elicitation of agreement in persuasion. Journal of Personality and Social Psychology, 21, 159—165.