Focus on the amygdala
In one study by Jaclyn Ronquillo and her colleagues, eleven young, white males underwent functional magnetic resonance imaging (fMRI) while being shown photographs of faces with varied skin tones. When they viewed black faces, it resulted in greater amygdala activity than when they viewed white faces. Amygdala activation was equal for light and dark black faces, but dark-skinned white people had greater activation than those with lighter skin tone. The authors concluded that Afrocentric features drove an unconscious fear response in white participants.
More recent imaging research has supported the intractable nature of prejudice in the human psyche. Chad Forbes and colleagues found that even self-reported non-prejudiced subjects could be prejudiced in some situations. White study subjects had increased amygdala activation while viewing images of black faces when they were listening to violent, misogynistic rap music, but not when listening to death metal or no music. Interestingly, they found that a region of the frontal cortex – an area of the brain expected to tamp down amygdala activation – was also activated.
The researchers speculated that the music reinforced a negative stereotype about black subjects, creating a situation in which the white subjects were not able to temper their prejudiced emotions. In fact, the authors speculated that the frontal cortices – generally thought of as areas of “higher” brain function – were instead recruited to help justify the feelings of prejudice felt by the participants listening to rap music.
Other research has shown that the amygdala response to out-group faces is not strictly bound to characteristics such as race. The amygdala responds to any out-group category, depending on whatever someone deems is salient information: your sports team affiliation, gender, sexual orientation, where you go to school, and so on.
Brains can control bias too
The Forbes et al study highlights that our ability to control reactionary implicit bias is dependent on the frontal cortices of the brain. A particularly important region of the cortex is the medial prefrontal cortex (mPFC).
The mPFC is the seat of empathy in the brain. It forms impressions about other people and helps us consider other perspectives. A lack of mPFC activity is associated with prejudice marked by dehumanization and objectification of others. For example, it is known that mPFC activation increases when we view a person of high esteem or prestige – for example, firefighters or astronauts – but not when we view someone marked with disregard or disgust, such as a drug addict or homeless person. Men with highly sexist attitudes have less mPFC activity when viewing sexual images of female bodies. These men also believed sexualized women have “less control over their own lives.”