American scientists have developed a brain scan that they say can detect people harboring racial prejudice. In racially biased white people who were shown photographs of black faces, the researchers found surges of activity in a brain region known to control thoughts and behavior, which they say are due to suppressed prejudice.
The research has already provoked controversy, with some experts arguing the study's conclusions are misplaced. At its most far-reaching, the study raises the possibility that the minds of people, including police recruits, could be screened for racist attitudes.
The scientist who led the research admits she was stunned when she saw the results. "I was shocked. I couldn't believe we got this correspondence with the brain activity," said Jennifer Richeson, a neuroscientist at Dartmouth College in New Hampshire.
Richeson said the brain activity arises because the volunteers are concentrating on not doing or saying anything offensive. This inner struggle tires the brain so much, she said, that prejudiced white people who interacted with black people would find it difficult to concentrate afterward.
"If they had an interaction that was hard to negotiate and then went back to work, they might not be able to focus on the task they're doing because they're exhausted," Richeson said.
To conduct the research, her team first asked 30 white students to take an implicit association test (IAT), in which they associated white or black names with positive or negative words. The test is contentious, but it is widely used as a convenient measure of unconscious or automatic racial bias. The students were not told what the test was about. They then briefly met a black or white person before being asked to complete a difficult mental task. Two weeks later the same students were asked to help in an unrelated experiment, in which they were handed pictures of the faces of black or white people while having their brains scanned with functional magnetic resonance imaging (fMRI) equipment.
The scientists found a strong link between a volunteer's IAT score and activity in a region of their brain called the right dorsolateral prefrontal cortex. Those with the highest levels of brain activity also performed the worst in the difficult mental task.
"The people are working hard to negotiate the interaction and then they're spent. It's almost like depleting a muscle: if you work it out too much then you can't lift any more weight," Richeson said.
Others say it is dangerous to interpret the results that way.
"That's exactly the kind of inference we're arguing it would be unfortunate to draw at this point," said Bill Gehring, a psychologist at the University of Michigan. "There just isn't enough known about what this task is actually showing."
The controversial study is published today in the journal Nature Neuroscience, which also discusses it in an editorial as well as publishing an accompanying article trying to explain the context.
"This study is likely to be widely discussed, so it is important to emphasize that it is not about biological determinants of racial prejudice," the editorial says. "Although it describes neural correlates of implicit bias, it says nothing about the source of this bias; even more importantly it says nothing about the relationship between implicit bias and actual behavior toward people of other races."