Cialdini Principles of Persuasion Series – Principle 3: Social Proof

March 31, 2015 | blog | By Mike Sullivan

We continue our Cialdini series this week by introducing social proof, a most exciting principle of persuasion in today’s digital marketing world. From psychology’s standpoint, social proof can be thought of as a “phenomenon where people assume the actions of others in an attempt to reflect correct behavior for a given situation.” From a pure marketing standpoint, it’s actually “if someone else has done it or used it and talked about it online, that’s social proof.”

Your customers will be influenced by what other people and companies are saying about your brand. It’s just human nature for us to have our opinions swayed based on what trusted sources are saying.

Social proof can come in the shape and form of many different elements …

  • Social shares on social media
  • Testimonials on your website, both written and video
  • Customer reviews and ratings
  • Trust symbols or verifications
  • PR

If your brand is being used by a variety of credible individuals or organizations, you’re in great shape. More people are likely to do business with you, buy your product or service, and follow your brand.

Let’s look at some inspiring examples of brands that are already using the power of social proof to rack up more sales.

Desk.com Racks up Some Amazing Testimonials

Desk.com, which was acquired by Salesforce a few years back, is a producer of out-of-the-box, customer service solutions for businesses. It competes with the leader in its space, Zendesk, for a bigger share of the customer-service software market. Because it doesn’t have an unlimited budget, Desk.com’s people had to come up with a practical way to persuade leads to choose their solution.

What they came up with is showing written testimonials right on their homepage. This way, leads and site visitors can see immediately what problems Desk.com’s software solved for them.

The company also scored big on another best practice of written testimonials: All testimonials link to specific case studies, so curious leads can read exactly how Desk.com helped those businesses make more money. Brilliant!


Challenger brands may not be able to outspend their industry leaders, but with clever and skillful use of testimonials, they can harness social proof to persuade people into choosing them in droves as their solution.

LOOMIS Imagibrand Process

Buffer Wants You to See How Many People Rely on It


Buffer is the social media app that empowers businesses to grow their social media fan bases by managing their updates more efficiently than ever. In a short time, this startup has gained a lot of users and runs one of the most popular marketing blogs ever. Because it’s done so well in just such a short period of time, the company naturally wants everyone to understand this—which also cleverly segues into using social proof as a means of persuasion.

On the Buffer blog, you’ll see two instances of social proof when you scroll down to the bottom of the page.

The first relates to the company’s email subscription sign-up. In the sign-up form, Buffer mentions that already more than 42,000 people receive its social-media best practices in its email newsletter. This communicates that more than 42,000 people already find Buffer a highly reputable source for social-media tips, which is powerful advertising. Using big numbers like that is also very persuasive.

Buffer delivers actionable social media advice

Buffer also has a super-effective call to action on the bottom of the page; this one prompts people to start using its app as a way to improve their social-media prowess. The headline above the call to action button brags that more than 2 million folks have already used and benefitted from the Buffer app. Again, this is perfect social proof since it demonstrates that all those people have approved and endorsed Buffer for their social-media use!

Buffer is adept at using social proof

Captain Kirk Enjoys Using Priceline

We’re all familiar with William Shatner, forever overshadowed by his Captain Kirk role from Star Trek. These days, he’s featured in Priceline’s ads and has been for many years. Priceline is in the online travel agency market, competing with the big dog in that group, Expedia, which owns 40% of this market. Priceline wanted to do something nifty and different instead of spending a lot of money to bombard the market with routine ad after routine ad.

William Shatner is Priceline's pitchman

So it went and got William Shatner as its pitchman. Getting a cultural TV icon, who’s known beyond merely the community of overexcited “Trekkies,” is solid social proof because it’s like getting an endorsement from someone who’s larger than life. Since Shatner’s fame goes beyond just Star Trek, having him star in Priceline’s commercials makes the company relatable to a wide audience.

Here’s a new Priceline ad starring Captain Kirk. Note how it also uses humor to connect with its audience.

Promoted Tweets Encourage Social Proof

Finally, I want to talk about promoted tweets, which is a revenue-generating model that Twitter came up with a couple of years ago. Promoted tweets are virtually tailor-made for challenger brands because they encourage social proof to happen on social media as a result of target-audience marketing.

Here’s how it works: Businesses can purchase promoted tweets and announce a new product, service or promotion. Then, they can use targeting options to connect with their appropriate audiences. These people will see these promoted tweets in their home timelines.

The implications of promoted tweets are nearly endless. Let’s say your fans see your challenger brand’s promoted tweet in their timeline…which gets them excited about a new product, service or promotion you’re launching. They then share this with everyone they know by a quick retweet. Let’s say this happens hundreds of times! Talk about massive, social-sharing action.

Papa John’s is a challenger brand to Pizza Hut, seeing as it’s the 3rd-biggest pizza-delivery chain and take-out restaurant in the world.

LOOMIS Agency promoted Tweet for Papa John's Pizza

Its promoted tweet cleverly alerted its target audience to the amazing availability of heart-shaped pizzas on Valentine’s Day. Talk about a highly relevant promotion! The tactical use of a promoted tweet together with beautiful timing for Valentine’s Day resulted in almost 1,000 retweets! Now that works out to some serious social proof for the whole world to see.

Your Customers Are Social Creatures

People are social creatures and so are your customers. Never forget that your customers are people first and customers second. That’s why persuading them with people power, so to speak, is an ingenious way to market to them. As the many challenger brands featured above know, using social proof is a successful way to build credibility, sway undecided leads, and rack up more conversions and sales.

We’re already halfway through our exciting Cialdini series, but now things are really just heating up. Stay tuned for next week’s blog post on the fourth principle of persuasion: authority. It’s going to be another actionable and tip-heavy piece…with a few surprises thrown in for good measure!


challenger brandcialdinisocial proof

Mike Sullivan

President at LOOMIS, the country’s leading challenger brand advertising agency


We challenge underdog brands to think differently. We help them find their voice, and urge them to blaze new trails to make sure they stand out from the pack. Whether you need an agency of record or support on a project, we are here to help you win.