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.

Friday, February 14, 2014

You thought you were really discerning didn't you?

As technology progresses, we have come to do more and more online, and this includes our shopping. Last Christmas 61% of Britons did more than half of their gift shopping online (Moth, 2014). As the internet becomes a new frontier for shopping, companies need to adapt their selling techniques – having a cute shop assistant is no longer going to be enough to seal the deal; they need to wise up.

The concept of social proof is discussed by Robert Cialdini in his 2007 book, ‘Influence: The psychology of persuasion’. He states that social proof is the idea that we are more likely to be persuaded or comply with a person or idea if we believe that our peers are doing it too. This principle is pretty much common sense, and operates much like it says on the tin; once we have proof that others are doing it, we believe that it is a more acceptable thing to do ourselves.  You’ve seen all of the TV shows and films, when teens are trying to persuade their friend to do something reckless and stupid, and so use the phrase ‘everyone’s doing it!”  - works like a charm.

With this in mind, Amblee and Bui (2011) looked into ‘harnessing the influence of social proof in online shopping: The effect of electronic word of mouth on sales of digital microproducts’.  They studied the online shopping titan '', and here they defined the principle of social proof as e-word of mouth (eWOM), when people left reviews on the product’s webpage. Surely if someone could be bothered to write and leave a positive review then it was a good sign and we should buy it too?

They had many hypotheses, but I am going to concentrate on one in particular; that ‘digital microproducts with customer review(s) will have better sales than those without any reviews’. In order to investigate this they compared the sales ranks of both groups of products (with reviews vs. without reviews) as can be seen by the chart below. They found that those without reviews had a much higher sales rank than those with reviews. Puzzling you think? The sales ranks are inversely related to the total sales of the product, meaning that the lower the sales ranks, the higher the amount of actual sales. They believe that these results ‘suggest that, on average, when one of the products got reviewed, its sale rank increased by 442,141 rank points.’ This clearly demonstrates the power of eWOM on the likelihood of people to buy products.

If you have ever bought anything from the Amazon website, you will most likely receive an email much like the one below, asking that you write a quick review of your recent purchase. Even if you don’t want to write a review, just ‘start by rating it’.  In this way Amazon are increasing their sales by manipulating the principle of social proof, if ‘LucyBerkeley4’ gave the product four stars how could you not buy it?


Amblee, N., & Bui, T. (2011). Harnessing the influence of social proof in online shopping: The effect of electronic word of mouth on sales of digital microproducts. International Journal of Electronic Commerce, 16(2), 91-114.

Cialdini, R. B. (2009). Influence: Science and Practice (5th ed.). Boston: Allyn & Bacon.

Moth, David. "One in Five US and UK Consumers Did All of Their Christmas Shopping Online: Stats." Econsultancy. Econsultancy, 06 Feb. 2014. Web. 13 Feb. 2014.

By Lucy Berkeley

1 comment:

  1. Great Lucy, you have combined a blog tone with fun research!


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