Looking at myself in the mirror the other day (um... I mean, while I was flossing), I realized that I will never truly be able to prove that anybody else is capable of complex thought. Nobody can show with certainty that they aren't the only people in the world that can actually think. Interesting dilemma for a person. A couple of points that I drew from it:
1) It could be useful in rationalizing racism. The more people look like us, the more likely we are to believe that they are capable of complex thought (or really, any thought at all), because they look like the only person we have ever seen engaged in complex thought (ourself, in a mirror). The less people look like us, they less we believe that they are able to think about things.
2) Realizing it opens you up to your own narcissistic tendencies. All of us have looked at other people and judged them. I know I have. However, somewhere in the back of my mind, I was probably also judging them because I subconsciously didn't believe them to be capable of thinking. But really, they have been thinking about all of this stuff. Any judgment that you can make about a person is undoutedly a million times more complex than you first judge it to be.