The Harvard study, published in the journal PLOS ONE, used real-time brain scans to pinpoint the region in which patterns of neural activity change when people look at black and white faces, and at male and female faces.
“We found that a brain region called the fusiform face area, or the FFA for short, seems to play a key role in differentiating faces along these two dimensions,” said Harvard Ph.D. Juan Manuel Contreras, the study’s first author.
“When we studied the patterns of activation in this region, we found they were different for black and white faces, and for female and male faces.”
But even though the brain seems to immediately collect information about race and sex, Contreras said, it’s not until later in visual processing that meaning is attached to those differences.
“It’s important to note that previous research suggests the FFA does not endow visual stimuli with meaning, so it probably does not know anything about sex and race. It’s simply a brain region in the visual system that sees faces as belonging to two different sets,” Contreras said.
“The information is simply being gathered, and is then handed off to other parts of the brain that begin to process what those differences mean — other regions that have information about what men and women are like or what it means for a face to belong to a black person or a white person”
To understand how the brain gathers that information and begins to process it, the researchers used functional magnetic resonance imaging, or fMRI, a technique in which researchers can monitor real-time changes in blood flow in the brain.
Once participants were inside the scanner, they were shown a series of images on a computer screen. The participants were asked to identify whether the faces were male or female, or whether the faces were black or white.
“We take images every few seconds,” Contreras explained. “Using statistical analysis, we can identify patterns of neural activity that correspond to different social categories. We could then look for differences in those patterns between the faces of blacks and whites, and between the faces of men and women.”
“We also found evidence that, when we asked participants to pay attention only to the sex of a person, this region was still recognizing race. When we told them to pay attention to race, the FFA was still recognizing sex, so it appears as though this region is constantly categorizing faces by sex and race.”
The question now facing researchers, Contreras said, is why.
It’s possible that, whether for evolutionary or developmental reasons, it is important to know the sex and race of other people, especially in situations in which these differences would change the way in which you interact with them.
“Sex and race can be important things to know about another person, so it would make sense that as soon as you see another person, you need to know figure out the social categories to which they belong,” Contreras said.
“What’s interesting is that the FFA is also believed to be involved in some aspects of processing identity,” he added. “Obviously, characteristics that are inextricably linked to you, like your race and your sex, are part of identity. Other scientists have shown that we perceive identity by perceiving the sex and race of faces, and what we’re showing here is a sort of neural correlate of that. If this region is responsible for identity processing, it might make sense that it’s also responsible for recognizing race and sex differences.”
Source: Harvard University