Journalist Oobah Butler demonstrated the power of social proof when his restaurant became the top restaurant on TripAdvisor - despite not existing. Using fake reviews written by friends and acquaintances, the restaurant soon received booking requests from around the globe.
Pratkanis (2007) explains how social consensus provides informational influence, or social proof, about what to do, as "if others are doing it, it must be correct". It also provides normative influence, as we want to fit in with the groups to which we belong.
As the "reviews" were written by people similar and relatable to those reading them, they are more likely to be believed than if they were written by a food critic or restaurant owner who is dissimilar to the audience (Cialdini, 2007). This can be explained by Festinger's (1954) social comparison theory, which describes how people are more likely to evaluate their opinions in comparison to people they are similar to. Finally, having multiple sources increases influence more than having multiple arguments from one source, leading to more persuasion when the arguments are strong (Harkins & Petty, 1981).
Cialdini, R. B. (2007). Influence: The psychology of persuasion. New York: Collins.
Festinger, L. (1954). A theory of social comparison processes. Human relations, 7(2), 117-140.
Harkins, S. G., & Petty, R. E. (1981). Effects of source magnification of cognitive effort on attitudes: An information-processing view. Journal of Personality and Social Psychology, 40(3), 401.
Pratkanis, A. R. (2007). The science of social influence: Advances and future progress. New York: Psychology Press.