Social Proof

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Social proof is evident in the tendency for people to follow the behavior of the herd, especially in circumstances that are uncertain. This course begins by introducing students to the strange phenomenon of social proof, highlighting circumstances where it is or is not a powerful influence on behavior. Next, it stresses that even in cases where social proof is a significant dictator of behavior, it can be extraordinarily difficult to detect. Finally, the course ends by discussing how social proof can be leveraged in practical and important ways—which students are encouraged to try for themselves. The following videos, visual aids, and websites comprise each unit of the course.

Narrative Overview

If lots of people say it’s good, it must be good. Social proof is the tendency to adopt the most popular behavior because its social clout seems to suggest it is the best, correct, or most acceptable behavior. Social proof is evident in “liking” on Facebook, in foot traffic patterns across campus, and in the tradition of a certain sports rivalry between Duke and a school down the road. On a daily basis, we experience social proof each time we do something simply because other people are doing it. This course examines the circumstances in which social proof influences our behavior, the difficulty we have detecting this influence, and the ways we can use social proof to our advantage.

Social proof becomes most powerful when people are uncertain of how they should act. On the first day of one of his large lecture classes, Professor Dan Ariely exploited this relationship between uncertainty and social proof for surprising and comedic effects. He began class by taking five minutes to read “a formal definition of behavioral economics.” The definition, it turns out, was total nonsense—and yet students remained in their seats and nodded along. Not one spoke up to voice his or her confusion. Professor Ariely calls this “pluralistic ignorance,” which is the phenomenon whereby “if you see lots of people doing nothing, you are going to do nothing as well.” Importantly, this exemplar of social proof becomes most powerful when social norms are ambiguous. Professor Ariely astutely chose to play his prank on the first day of class. Further into the semester, students familiar with his teaching style would have been more likely to raise their hands and question his strange behavior.

What is perhaps most surprising about the phenomenon of social proof is just how persuasive it can be. That is, extremely subtle social manipulations can lead to significant effects on our behavior. Professor Noah Goldstein describes how changing one line of text in an infomercial—from “operators are standing by” to “if operators are busy, please call again”—can drastically increase sales. Counter to our intuitions, the latter line is more successful at garnering calls because it suggests that many other viewers are also interested in the product. Callers are persuaded simply by the notion that other people are also calling in.

Despite the powerful role that social proof plays in guiding our behavior, we often fail to detect it. Each winter, hundreds of Duke students sleep in line for over a month on the “Krzyzewski-ville” lawn in order to secure their seats at a basketball game against Duke’s rivals, the UNC Tarheels. When asked why they are willing to go to such great lengths to get into the game, students initially report that they “love Duke basketball.” However, when pressed to explain further, many of these students admit that they were not interested in the sport before coming to Duke. Some had not attended any games prior to the one they were tenting for. They decided to tent not necessarily out of a passion for basketball, but rather, because tenting is itself a part of “the Duke experience.” Duke students sense this as a social pressure that is difficult to articulate. In the words of one tenter, “it’s something everybody kinda has to do.”

Professor Goldstein has formally studied the failure to detect social proof in an experiment he conducted in hotel bathrooms. Prior to his experiment, most hotels encouraged guests to reuse their towels with placards that touted the benefits for the environment. Professor Goldstein imposed a subtle manipulation that utilized social proof—rewording the signs to report the percentage of guests who had reused their towels when they stayed at the hotel—and found that people were significantly more likely to reuse their own towels. Yet, when surveyed, people report that environmental factors are very important to their decisions about recycling, while they believe that the number of people recycling is a trivial factor in their decision making process.

This experiment suggests an important way that social proof can be leveraged to persuade others. Browsing the great variety of signs posted around Duke’s campus, we found that most were like the original placards at the hotel. For instance, signs instructing people to wash their hands provided information about the flu and norovirus. These signs would be significantly more effective in guiding behavior if they applied the principle of social proof. That is, signs for hand washing should report the (relatively small) percentage of students that went to student health for these viruses last year and encourage you to be part of the hand washing majority.

When made aware of social proof, it becomes easier to detect and to use to your advantage. As you go through your day, think of all the ways that social factors may be guiding you to do things you otherwise wouldn’t do. Try not to follow the herd when it is misguided, while joining others to support causes that you believe in. You may even consider using social proof as tool to encourage others to follow your lead. In fact, 74% of students who have taken this course decided to revamp one of the signs they see every day using the principles of social proof!

Watch VIDEO: Social Proof (Part 1 of 3)

“Gangnam Style”flash mob

Introduction to social proof from “Persuasion: Provincial Norms” by Noah Goldstein

Pulp Fiction social experiment, based on this clip

Word clouds of student responses to the ‘Pulp Fiction’ clip:

Cloud - Laugh Track - Edited3

Cloud - No Laugh Track - Edited3

Watch the VIDEO: Social Proof (Part 2 of 3) to see why these two groups of students reacted in different ways to the clip!

Duke basketball and the Cameron Crazies

Real and perceived reasons for tenting in K-Ville

Experiment on recycling hotel towels from “Persuasion: Provincial Norms” by Noah Goldstein

Bonfire following a win over the UNC Tarheels

Signs posted around Duke’s campus

Ways to leverage social proof from “Persuasion: Provincial Norms” by Noah Goldstein

Time lapse of student activities at Duke

Signs revamped using principles of social proof

Signs before applying social proof:

Signs Before

Signs after applying social proof:
Signs After

Reading and Activities:




  • All videos related to the course are compiled on our YouTube channel
  • For up-to-date information and news on social proof, check us out on Facebook

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