Social psychologists have long known that human beings often make choices about what to think, and what to do, based on the thoughts and actions of others. Simply stated: We like to follow the crowd. As a psychological phenomenon, it's called &quot;social proof.&quot; And according to Robert Cialdini, the Regents' Professor of Psychology and Marketing at Arizona State University and Distinguished Professor of Marketing in the W. P. Carey School, &quot;social proof&quot; is one of the six key principles underlying the powerful science of persuasion.<br><br><a href='http://knowledge.wpcarey.asu.edu/index.cfm?fa=viewArticle&amp;id=1347&#039; target='_blank'>http://knowledge.wpcarey.asu.edu/index.cfm?fa=viewArticle&amp;id=1347&lt;/a&gt;&lt;br&gt;&lt;br>