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How to Be Persuasive: Social Proof

We’re in the middle of a conversation about the importance of persuasion by working through Robert Cialdini’s book, “Influence: Science and Practice,” and his six principles for being persuasive. We’ve already looked at Reciprocation and Commitment and Consistency, discussed how they are used in society, and gave you some ideas about how to apply them.

The next principle is Social Proof—one of my favorite concepts to discuss. Social Proof is the idea that humans find safety in numbers. I also call this the “standing in line” principle, which I’ll explain in a moment.

I first encountered this idea while studying consumer behavior in business school. I was looking at the unique business models the internet and computer algorithms have made possible in the last few years. One of the companies was the online consignment store Twice. Its founders, Noah Ready-Campbell and Calvin Young, are Google alumni who wanted to use their algorithm-writing skills to help people. They wanted to enable people to buy nice clothes for a fraction of the retail value.

Here’s how it works: If you want to sell clothes, Twice will send you a pre-paid shipping bag, you load in the clothes (if they follow Twice’s guidelines), and you drop it in the mail. Twice gets the bag of clothes, decides what they can sell and what they can’t, and they make you an offer. If you accept, you get paid immediately, and the clothes they don’t use are sent to charity. If you reject their offer, you can get your clothes back by paying for shipping.

The first time I sold clothes to Twice, the bag came with a few pieces of instructions. One of them asked me to write down how many items I put in the bag. It also said, “the average seller sends us 19 items”. This is a great example of social proof. If you were about to send in 20 items, and were wondering if that was too much, now you know you are normal and will probably go ahead with sending the 20 items. If you were about to send 12 items, you might consider sending more.

It’s in Twice’s interest for you to send in more items, because it makes it more cost-effective per bag. It could also be in your interest as well, if you make more money for your clothes.

I also call social proof the “standing in line” principle because we see the phenomenon of people standing in line everywhere. From people waiting for days for the next Apple product, to people getting in the wrong lines at grocery stores, understanding how lines work is a very real problem for retailers.

You might think that people would always look for the shortest line, but that’s not always true. People want to be where they think they are supposed to be, which is usually believed to be where everyone else is. So believe it or not, people will get in line behind others often before they look for a shorter line. That’s why you’ll always hear grocery store cashiers yelling that their line is open.

One more example: The first time I took an Amtrak train, I didn’t know where I was supposed to be to get on the right train. It turns out that most of the other people didn’t either. Much to the staff’s chagrin, people started lining up at the wrong door and wrapped the line around in the wrong way.

Even people who take the train all the time got in this incorrect line. After the staff got us straightened out, I heard a regular traveler say that he thought someone was wrong with the line but he didn’t want to say anything.

People are comfortable in numbers, so think about how you can add this effect when trying to be persuasive. Whether it is actual numbers of people in a line or in a room, or simply telling them about numbers of people—making them feel like they are in good company, social proof can be one of the most helpful of Cialdini’s principles.

Have you experienced or used this principle? We’d love to hear about it in the comment section below. The next principle we’re going to look at is Liking.