What is social proof theory?

In Blog by Iranzu Monreal

11th Aug. 2021

By Hannah Chappell


What is social proof theory?

Imagine you’re at the grocery store picking up some essentials. As you head to the till, you notice that the store has partnered with a local charity and is collecting donations. The cashier asks each of the customers before you whether they would like to make a donation; all of them say yes. When you step forward to pay, the cashier poses the same question, and you agree. Now consider: to what extent did the responses of those before you influence your decision? 

It is common knowledge that humans are social creatures: we live in close quarters, seek opportunities to build relationships, and maintain a close watch over our social standing at any given time (‘the cooperative human,’ 2018). The connection between the individual and the collective is sufficiently powerful as to influence human behaviour in myriad situations. This phenomenon, known as social proof theory, means we often look to others' actions in order to determine the appropriate behaviour in a given situation (Cialdini, 1984). Moreover, deliberately communicating social norms—in other words, the expected behaviour in a given context—can significantly influence people's subsequent actions (Perkins & Berkowitz, 1986). 

Consider, for example, paying taxes. Individuals are more likely to submit payments if tax compliance is presented as the morally correct and expected behaviour and if individuals believe that others are also paying their taxes (Bobek, Hageman, & Kelliher, 2013; Jimenez & Iyer, 2016; 'Using social norms to increase tax compliance,' 2016). Here at The Behaviouralist, we have successfully used social norms messaging to boost council tax compliance within the London Boroughs of Enfield and Haringey.

However, when it comes to encouraging tax compliance and other socially desirable behaviours, the language and structure of norm messaging are key. Descriptive norm messages communicate what behaviour is prevalent in a given situation (e.g., what most people are doing), while injunctive norm messages describe what should be done in a particular scenario (Bicchiere & Dimant, 2019; Shultz et al., 2007). Behavioural scientists also distinguish between dynamic norms, which indicate how people's behaviour is in the process of changing, and static norms, which describe the normative behaviour as it currently is (Sparkman & Walton, 2017). Moreover, different types of normative messaging have been found to affect behaviour differently. For example, personal norms (individuals’ own standards of behaviour) and subjective norms (the behavioural expectations of others) have been found to directly influence tax compliance, whereas descriptive and injunctive norms are more likely to indirectly affect taxpayer behaviour by activating other normative constructs (Bobek, Hageman, and Kelliher, 2013). As a result, behavioural change interventions should be designed with an eye to the diverse results that norms can generate.

Across industries and sectors, norms are frequently used in advertising campaigns. Consider this recruitment poster from World War II:


Though the message and graphic are simple, their intended effect is abundantly clear, even to a contemporary viewer. Here, following the norm entails joining the many who have already volunteered to defend their country. 

More recently, social norms have been used to encourage behavioural practices that prevent the spread of COVID-19:


This graphic, distributed by Colorado State University, underscores that wearing a face covering is a social, reciprocal activity. It draws on descriptive norms to convey that the vast majority of students are already practicing these protective behaviours, thereby informing others that this is a socially-expected behaviour.

Social norms are rife in commercial marketing. Consider this Australian advertisement from Oral-B:


The advert takes care to emphasize that Australia as a collective has adopted this product. Viewers are encouraged to 'go pro' and join their fellow Australians by purchasing this particular toothpaste. 

But the question remains: why do norms have such potent effects? Evolutionary psychologists posit that our tendency to follow norms is an innate feature of our social psyche, which historically increased our chances of survival and reproduction (Alexrod, 1986; Gavrilets & Richerson, 2017). This perspective is supported by findings that norms are more salient and impactful when they refer to a group with which we identify: in order to maintain our protected, in-group status, we tend to follow the common practices of our collective. Nevertheless, the questions of why and how social norms affect us so strongly in today's world merit further investigation. 

We will be examining this topic further in the coming weeks, delving into Wikipedia's perplexing norms-based donation campaigns, cutting-edge research, and more. Follow The Behaviouralist on LinkedIn and Twitter to receive updates on these and other future posts!