Found this article in Scientific American to be pretty interesting read, worth a few minutes to get the studies details:

"How does the brain differentiate those who are similar to us from those who are different? Does it analyze differences in skin color, language, religion, height, eye color, foot size?

In a way, the brain does all this and more by simply distinguishing those who don’t meet various definitions of who we are. Specifically, a forebrain area called the dorsal medial prefrontal cortex (mPFC) appears to predict the behavior of members of outgroups by employing prejudices about their presumed background"

and they concluded:

"that a critical strategy for reducing prejudice may be to breach arbitrary boundaries based on social group membership by focusing instead on the shared similarity between oneself and outgroup members." This is not new advice. Yet it is heartening to see that it is firmly grounded in distinct patterns of neural activity. There may be a brain basis for reacting with prejudices for those that seem different. But there’s also a brain basis for overriding those differences and seeing outsiders as more like us."