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, February 19, 2014

Buy now, before it's gone

‘While stocks last’, ‘Sale ends soon’, we’ve all observed shops warning us that products are of limited availability, attempting to lure us in to purchase their endless supposed deals. TV shopping channels spend little time telling us about the item, instead bombarding us with endless warnings that the product won’t be on sale for much longer.
Brock (1968) referred to it as the commodity theory, whilst Cialdini (2001) included as one of his six weapons of persuasion. Whilst giving it different titles, they both referred to the same idea; we as consumers want what we believe to be less available. The theory states that if a commodity is scarce, or becoming scarcer, it is seen as more valuable, more desirable.
This is understandable: as humans, we seek reasons for why things happen. So if we notice that a certain commodity is less available than another, we often determine that there must be a reason for this, and often the reason we arrive it is that is must be popular, and therefore better than the alternatives with unlimited quantity.

Numerous researchers have demonstrated this scarcity effect. However, is there any more depth to this? Does the reason for its scarceness determine whether it’s still seen as more desirable?
Verhallen and Robben (1994) investigated this, looking at whether the reasons for the low availability would determine the preference for a recipe book, and whether the social situation the participant found themselves it had any effect on this.
Verhallen and Robben (1994) asked participants to rate and choose one of 3 recipe books. Within this, there was two main conditions, one where the participants were lead to believe that their preferences of recipe book had an effect on other peoples choices (Social constraint condition), and another whether there was no social constraint at all and they were told they were the last ones to pick.

Additionally there were further conditions which were about the availability of the different recipe books. Either the books could in unlimited supply, or supply was limited. Within the limited condition there were different reasons for scarcity; it could be due to accidental circumstances, popularity, limited supply, or popularity and limited supply together. The final two (either separately, or combined) are termed market causes.

After testing 120 people, results of this experiment showed that the reasons for an items scarcity do have an effect on choice. For instance,  if we look at table 1 below, items which were of limited availability due to market reasons (popularity, limited supply, or both of these combined) were significantly more likely to be ranked as the first choice of book than the items which were either of limited availability due to accidental circumstances, or that had unlimited availability. This finding, whilst interesting, was to be expected as it is fundamentally the scarcity principle as told by Brock, (1968).

An interesting finding within this experiment comes from comparing the social constraint condition with the no social constraint one. Though it was found that items with availability limited due to market causes are of greater preference in the no social constraint group, this effect was seen to disappear in the social constraint group. That is no significant relationship is observed. This demonstrates that the presence of others when making a choice will affect that choice, altering what we would perhaps have otherwise preferred based on the availability information present.

Scarcity sells. If we want to increase consumer desire for our product it is clear from the research that the idea that if they do not purchase it quickly it will no longer be available causes an increase in consumer desire for the item. However, this experiment would appear to suggest that social constraints can affect our decision even if the item is scarce.


Brock, C. (1968). Implications of commodity theory for value change. In A. G. Greenwald, T. C. Brock, & T. M. Ostrom (Eds.), Psychological foundations of altitudes. New York: Academic Press.

Cialdini, R. B. (2001). Influence: Science and Practice. Boston: Allyn & Bacon.

Verhallen, T. M. M. & Robben, H. S. J. (1994). Scarcity and preference: An experiment on unavailability and product evaluation. Journal of Economic Psychology, 15, 315-331.

Aaron Chaloner


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