People have a tendency to fear members of races other than their own, although intimate interracial relationships help to mitigate those biases, a recent study suggests.

“Both white and black Americans exhibited a bias toward fearing strangers of another race,” Jeffrey Ebert, a psychology graduate student at Harvard and co-author of the study, wrote in an e-mail. “For whites, this meant they developed a stronger, more persistent learned fear response to the face of a black stranger; for blacks, this meant more robust learned fear toward a white stranger.”

The study also found that bias against members of other races was significantly reduced among those who have had an interracial dating experience.

Researchers presented black and white subjects with images of two black and two white males. During the presentation of one of the black faces and one of the white faces, subjects were administered a mild shock. The shock was designed to condition the subject to fear the two faces. Fear responses were measured through increases in the activity of sweat glands, which offered researchers a window into subject’s emotional state.

Subjects were then presented all four faces a second time, without the administering of any shock. This time researchers found that the fear response—activation of the sweat glands—to “the face from the participant’s own race diminished, while the response to the face from the other race persisted,” Ebert said.

Because subjects with a history of interracial dating saw almost no persistent fear reaction to the faces of other races, the study’s authors—Ebert, Cabot Professor of Social Ethics Mahzarin R. Banaji, New York University (NYU) Professor of Psychology and Neural Science Elizabeth A. Phelps, and NYU graduate student Andreas Olsson—concluded that fear learning is influenced by one’s social group, and thus may be socially conditioned.

“Individuals acquire negative beliefs about outgroups according to their local cultures, and few reach adulthood without considerable knowledge of these prejudices and stereotypes,” the study concluded.

Rather than representing an aversion to peoples of another race—interaction between races is too recent for such a response to have evolved—the results suggest that “humans might have evolved a more general preparedness to fear others who were dissimilar to them or who otherwise appeared not to belong to their social group, because such individuals were more likely to pose a threat,” according to the study.

“Most of the research I have done shows that we humans are not the nice people we think we are,” Banaji wrote. “We should not assume that we will be ‘fair’ in our fear responses. We are likely to fear members of outgroups who have done us harm more so than members of our own group who have done us equal harm.”

She said, however, that the fact that interracial dating reduced fear responses indicates that, through interaction, fear of outgroups can be reduced.

Banaji also wrote that her study has policy implications that are particularly timely for Americans today.

“In our times of terrorism, we need to be alert to the fact that our fear of an unfamiliar terrorist may persist longer than our fear of an equally lethal home-grown one such as a Timothy McVeigh,” she wrote.

—Staff writer William C. Marra can be reached at wmarra@fas.harvard.edu.