Social proof is a term used to describe our tendency to follow the behavior of others. This tendency is amplified if we are uncertain about the situation. Social proof generally guides us into making fewer mistakes—if many folks are doing something, it’s usually the correct thing to do. However, this “auto-pilot” behavior can be easily exploited to manipulate our decision making process. For instance, to lead us towards a decision that serves someone else's interests or is incorrect.
Laugh tracks in TV shows and hired clappers in a theater performance can trick us into perceiving the content to be funnier or higher quality than it actually is.
Testimonials increase our likelihood of buying a product, especially when they indicate popularity. Terms like “best selling” or “recommended by 9 out of 10 professionals” are marketing applications of social proof.