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.

Thursday, January 29, 2015

Vegan-friendly Persuasion and Influence

Every Tuesday from 12pm to 5pm in the Warwick Students' Union Atrium, some wonderful students from the People and Planet society run a stall called the Food Coop, a social enterprise which buys products wholesale in order to sell them on to students at affordable prices. The products are ethically sourced, organic and many are useful ingredients in vegetarian or vegan diets. The stall also features locally-sourced honey, you can order boxes of vegetables and now even bread from a local bakery. The Food Coop however depends on members volunteering to run the stall every week; how do the volunteers sell this membership? Through the ‘That’s-not-all’ (TNA) technique, of course.

Pollock, Smith, Knowles and Bruce (1998) replicated the effects of TNA (found in Burger’s classic 1986 study). Experimenters tried selling small and large boxes of chocolates to passersby on a college campus. Subjects could either buy a small or large box of chocolates, for $1 or $5 respectively. In the TNA condition, subjects were told the small boxes were $1.25 but would be sold to them for $1 and large boxes were $6.25 but would be offered to them for $5. Subjects were also either given no extra reason, a placebic reason or a real reason for them to purchase the chocolates during the experimenter’s sales pitch.

As seen in Table 1 below, Pollock et al. replicated the results of Burger (1986); subjects purchased more small $1 chocolate boxes in the TNA condition than in the control conditions, no matter what reason the experimenters gave the subjects, with an average of 76% of boxes sold in the TNA conditions compared to 45% in the control conditions. Pollock et al. (1998) concluded from this that the that’s-not-all technique contributes substantially to gaining compliance in simple sales situations. 

On a side note, Pollock et al. also investigated Burger’s (1986) findings with the intention to discover how one might avoid being influenced by the TNA technique. The bigger and more expensive $5 dollar boxes of chocolate did not see increased sales in the TNA conditions, as evidenced by the higher average of 24% of the boxes sold in the control condition compared to 18% in the TNA conditions. Pollock et al. (1998) concluded this was due to the $5 boxes requiring more mindfulness due to the higher price, suggesting TNA only works in sales pitches where the subject can be ‘mindless’.


When new customers approach the Food Coop stall, and one of the volunteers running the stall tries to persuade them to buy a membership, the volunteer tends to rattle off this checklist of perks:

·         “Membership costs just £5”
·         “But that’s a one-off payment for a lifetime membership”
·         “Once you’re a member you get a 10% discount on everything!”
·         “When you’re a member, you can order a veg box”
·         “And you can also order some awesome bread from a local bakery”
·         “Plus you can recommend things to sell at the stall”
·         “You can even come and volunteer behind the stall!”

By listing all these perks, the volunteer minimises the perception of the £5 being a big commitment and progressively adds more and more benefits to having a Food Coop membership, so the new customer feels as if the Food Coop is doing more and more for them. This leads the new customer to feel they must reciprocate this effort and comply with the request to pay a £5 membership.

The Food Coop should heed Pollock et al.’s (1998) advice and maintain the membership price at £5, in order to prevent future customers becoming too mindful and immune to the effects of TNA. Some of them might also consider careers as presenters on infomercials. 


Burger, J., M. (1986). Increasing compliance by improving the deal: The that’s-not-all technique. Journal of Personality and Social Psychology, 51, 277-283.
Pollock, C. L., Smith, S. D., Knowles, E. S., & Bruce, H. J. (1998). Mindfullness Limits Compliance With the That's-Not-All Technique. Personality and Social Psychology Bulletin, 24, 1153-1157.

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