How White Brains Process Black Faces
Post by Anastasia Sares
What's the science?
Social identity theory, proposed by Henri Tajfel in the late 1970s, highlighted the fact that we tend to separate people into an “in-group” and an “out-group,” attaching our identity and self-esteem to the in-group. We focus on the positive qualities of our own group and the negative qualities of the out-group, which leads to discrimination, stereotyping, and unequal division of resources. Divisions can occur along racial, religious, political, and class lines (to name a few). One important feature of in-group/out-group dynamics is that we view people in our in-group as unique individuals while viewing people in the out-group as mostly the same.
In Proceedings of the National Academy of Sciences, Hughes and colleagues used functional Magnetic Resonance Imaging (fMRI) to show that self-identified White participants, on average, perceived Black faces as more similar (less distinct) than White faces. In their own words, “Our results suggest that biases for other-race faces emerge at some of the earliest stages of sensory perception.”
How did they do it?
Hughes and colleagues used a technique called neural adaptation. One might think of it as “the brain getting used to things.” Imagine you are being shown a series of faces. The first few are very engaging, but after a while, you may feel your attention wane. Your perception of the faces isn’t as sharp, and you might have trouble telling them apart. If all the faces are different and interesting, you might stay engaged, but if you’re shown the same face over and over again, you will quickly lose interest. We can watch this happen in the brain with fMRI. Over time, if a stimulus happens over and over again, the signal in the relevant brain area will decrease as the brain adapts, or gets used to, the stimulus. The rate of adaptation is slower for stimuli that are distinct from one another: in other words, the signal in the brain takes longer to decrease. On the other hand, the brain will adapt quickly to stimuli that are perceived as more similar, or as belonging to the same category.
In this study, the authors wanted to see how quickly the brains of self-identified White participants got used to seeing White faces versus Black faces. Using face-morphing technology, they created many different faces, making sure that the variability in visual features was exactly the same between the White and Black faces. Then, they measured the rate of neural adaptation in the participants’ brains for each group of faces. They focused on a brain area known for its sensitivity to faces: the fusiform face area. Following the fMRI experiment, they further tested participants on their ability to discriminate and remember faces.
What did they find?
To begin with, overall brain activity for viewing White faces was higher than for viewing Black faces in face-related brain areas. In the fusiform face area specifically, White participants showed more adaptation to the Black faces, indicating that the participants’ brains perceived these faces as less distinct. The follow-up tests were consistent with the neuroimaging results: most participants judged Black faces to be more similar to each other.
What's the impact?
Recent events involving racially-charged police violence have raised awareness of systemic racism in society. It is important to recognize that racial bias is built into perception in order to counteract it. The brain devotes more processing power to things that are familiar, and previous work suggests this is determined by exposure and experience. Research shows that we can combat our perceptual biases by changing the exposure factor - encouraging diversity in the workplace, media, and our social lives, and by raising awareness of these biases. Cognitive control may also play a role, so actively confronting our own racial bias may be another effective strategy.
Hughes et al. Neural adaptation to faces reveals racial outgroup homogeneity effects in early perception. Proceedings of the National Academy of Sciences of the United States of America (2019). Access the original scientific publication here.