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.

Wednesday, November 2, 2016


The scarcity principle suggests that when opportunities are in short supply, they become more desirable. We are more motivated by the thought of losing items compared to gaining items of equal worth (Tversky and Kahneman, 1981). Scarcity leads us to believe that items have more value than items in abundance and therefore become more desirable. This is due to social norms. 

Social norms are the rules written by society on how to behave, and govern our lives. We want to fit in with society and as a result become sheep. Scarcity is one way of highlighting popularity and therefore increases appeal. We subconsciously make the assumption that items are scarce due to it being popular, and by the rules of social norms if other people want it, we want it too. Therefore scarcity is proof of an items worth.

A study that cleverly demonstrates this principle was created by Worchel, Lee and Adewole (1975). In this experiment 200 undergraduate students were required to rate the value and attractiveness of cookies in two identical jars. In one jar the cookies were in an abundant supply (10), whereas in the other jar the cookies were in scarce supply (2). The results revealed that participants preferred the cookies that were scarce, supporting the scarcity principle. In a follow up study, cookies were either constantly scare or began in abundance then became scarce. Participants were also told that this change in availability was either due to an accident in which the cookies were spilt or due to high demand for the cookies. The results indicated that cookies are rated more favourably when they go from being abundant to being scarce compared to constantly being scarce. Cookies were also rated higher if the scarcity was due to high demand. This is proof that scarcity is a signal about the product. We believe that others must know something that we do not, so place more value in their judgement. We automatically assume that the cookies in the almost empty jar must be better for some reason, as scarcity is a form of social proof. The fact that cookies in scarce supply were only preferred when told it was due to popularity emphasises this point.

Overall the scarcity technique is good at inducing social proof, and is cleverly used by marketeers to increase sales. The technique suggests that people are motivated by what others have, and has been demonstrated in studies such as that by Worchel, Lee and Adewole (1975).


Tversky, A., & Kahneman, D. (1981). The framing of decisions and the psychology of choice. Science, 211, 453-458.

Worchel, S., Lee, J., & Adewole, A. (1975). Effects of supply and demand on ratings of object value. Journal of Personality and Social Psychology, 32, 906.

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