Social scientists say that there are reasons why we judge people based on how they look. On a very basic level, judging people by their 1 means putting them quickly into categories. In the past, being able to do this was vitally important, and humans developed the 2 to judge other people in seconds. Susan Fiske, a professor of psychology at Princeton University, said that 3, most stereotypes are linked to judging whether a person looks 4 or not. “In prehistoric times, it was important to stay away from people who looked aggressive and dominant,” she said. One reason why our brains persist in using stereotypes, experts say, is that often they give us generally 5 information, even if all the details aren't right.