Social Proof in the User Experience (Jennifer Cardello)

Social proof is a psychological phenomenon where people reference the behavior of others to guide their own behavior. This tendency is driven by our natural desire to behave “correctly” under most circumstances—whether making a purchase, deciding where to dine, determining where we should go, what we say, who we say it to, and so on. One of the best examples of social proof, in real life, is the long line in front of an Apple Store on the day a new iPhone is released. The fact that a group of people find the new phone so desirable as to invest considerable time standing (or sleeping!) in line impacts our perception of the phone value (and makes us covet one, too). (nngroup.com)