We’re more likely to work late if our colleagues are also burning the midnight oil, put a tip in a jar if it already contains money, or eat in a restaurant if it’s busy.

One of the most famous studies on social proof was conducted in the streets of New York City in 1969. A man simply stood, looking up into the air. He went completely unnoticed by passersby until the researchers increased the number of people (all staring upwards) to five, drawing a small crowd. But when they increased the number of participants to 18, the crowd multiplied by 400%!

In 2008, Robert Cialdini performed a study involving the placards in hotel bathrooms that urge guests to reuse towels. Over a threemonth period, he tested two different placards in a 190-room chain hotel: One card read, “Help Save the Environment” and urged visitors to “show your respect for nature” by reusing towels. The other card read, “Join Your Fellow Guests in Helping to Save the Environment” and also noted that 75% of guests participated in the towel-reuse program. At the end of three months, the guests who were exposed to peer pressure (simply from the text from the second card) were 25% more likely to reuse towels.

Figure 1: Crowdsourcing Products

Naked Wines also use Social Proof to sell their wines. In Figure 1, Modcloth uses Social Proof by asking shoppers to vote on future styles. Then they promote and merchandise these styles as a “be the Buyer Pick”. By soliciting and leveraging the opinions of their buyers, Modcloth saw a 2x uplift in conversions for those items.

Figure 2: Social Proof: Stats & Reviews Drive Purchase

Using a message that says,“90% of 4,814 would buy it again,” like in Figure 2, has proven to be pretty powerful. Leveraging the fact that people like to play it safe, James Bagley, Marketing Director, Naked Wines says that because many of their wines are from small, lesser-known estates, using Social Proof in their marketing has been a main factor that consumers rely on during their decision-making process.

Figure 3: Testing Social Proof

In June 2013, betting website Betfair performed a test based on Cialdini’s Principles of Persuasion. The goal was to increase clickthrough rates to their registration page.
They tested reciprocity (offering free tips and advice in exchange for registration), scarcity (using a “Don’t Miss Out!” messaging), and the social proof method (advertising their “Likes” on Facebook, shown in Figure 3).

While each technique worked better than the control, the social proof version drove the biggest improvement—with a 7% lift in clickthrough rates.