When we were kids, my friends and I made up a game we called “Made You Look.” Three or four of us would get fairly close together – in a shopping plaza, on the street, or anywhere there were lots of people – and look up as if we saw something incredible.

It would never fail. Passers-by would glance up to see what we were looking at. Some would stop and stand there for half a minute trying to discern the object of our attention. And the more of us doing it, the more people would look. One time in New York City, we did this with a dozen cohorts and virtually stopped traffic on Broadway.

We knew it was smart aleck juvenile humor. But what we didn’t know was that it was a classic demonstration of a powerful psychological principle called Social Proof. The idea behind Social Proof is simple: People are all copycats to some degree. We do what others do simply because others are doing it.