The scientists measured fear responses in the study participants through changes in their sweat glands, which indicated their emotional state.
"The fear response all depends on whether you're black or white," Banaji said. "If you're white, the fear response falls away more quickly to white faces than black. If you're black, it falls away more quickly to black faces than white."
Because the preference for one's own group was observed in both white and black participants, the results suggest that the fear response is not just about cultural learning.
"We know this is not something that could just be a stereotypical association of fear with African Americans, because each group shows the extinction [of fear] to its own group," Phelps, the NYU psychologist, said.
Evolution and Culture
So where does this fear of others come from? The researchers say evolution may be partly to blame.
"Millennia ago, when groups stayed segregated by tribes and clans, the association of difference with something bad or fear-provoking may have been reasonable or served a purpose," Banaji, the Harvard psychologist, said.
Humans may have developed a predisposition to associate people of a different social group with a negative outcome.
The fear has nothing to do with race per se, the researchers say, but only points to our fears of other social groups.
However, what we learn from our own group also influences our perceptions of other groups.
"There's no simple message, like it's all coming from the past, or it's all from learning," Banaji said.
"If we just say, All we need is to love each other, that would be a very naive story," she added. "If we assume that we are who we are because of what happened millions of years ago, that would not be accurate or optimistic either."
But the researchers do see a lesson in the fact that participants who had been in romantic relationships with a member of the other racial group shed their fears more easily.
In other words, spending time with people from another group can diminish the fear of others.
Arne Öhman, a professor of psychology at Karolinska Institutet in Stockholm, Sweden, wrote an article accompanying the study in Science. He says the study's findings are more relevant today than ever.
"The function of fear is to promote avoidance of potentially dangerous stimuli, and what you avoid you will not learn about," Öhman said. "Because you isolate yourself from corrective information, you may think that members [of other groups] are dangerous and evil in order to justify your fear, and in this way fear may breed interracial antagonism.
"We can see this mechanism at work in London today, where the fear produced by terrorists identifying themselves as Muslims is rapidly spreading to [a fear of] the majority of Muslims who strongly oppose fundamentalism," Öhman concluded. "Knowing the role of fear in promoting intergroup antagonism should make for restraint in what goes into tabloid headlines."
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