“You think of yourself as a person who strives to be unprejudiced, but you can’t control these split-second reactions. As the milliseconds are being tallied up, you know the tale they’ll tell: When negative words and black faces are paired together, you’re a better, faster categorizer. Which suggests that racially biased messages from the culture around you have shaped the very wiring of your brain.”
http://www.motherjones.com/politics/2014/11/science-of-racism-prejudice