Can brain imaging tell us anything about racism? Given the unfathomable political situation we find ourselves in today, we certainly need to consider every angle as we fight back against the ever louder proponents of racial separatism and violence.
But to be sure brain imaging is perhaps a stretch in this regard. Psychologists and psychiatrists are divided about whether brain imaging and other tools of neuroscience can add anything valuable to our understanding of complex human emotion and behavior. Some believe that brain imaging is the closest we have ever come to understanding how the living human brain works, whereas others point to inconsistencies in functional magnetic resonance imaging (fMRI) findings and bemoan the substitution of voxels for the human mind.
In that context, it is perilous to assert that neurobiology might be helpful not only in understanding some aspects of racial bias but also in figuring out how to overcome it. Yet a recent review of studies suggests that this is indeed the case. As we are now faced with increasingly strident signs of prejudice and relentless adherence to extremist in-group sentiment, brain imaging and other neurobiological studies suggest one silver lining: prejudice is at least in part a learned phenomenon that can be reversed by appealing to the proper parts of the human brain.
At least four different brain regions seem involved in the propensity for conformity to group racial bias: the amygdala, insula, ventral striatum, and the prefrontal cortex (PFC). The amygdala is well-known as critical for emotional learning and the acquisition of fear memory. Studies consistently show that when people are shown pictures of faces of out-group members, the amygdala is activated. Strikingly, this phenomenon tends to be more robust when the faces are unfamiliar and after subjects have seen them several times, less likely when the faces are presented too briefly for conscious registration, and modifiable by the set of instructions that subjects are given about how to think about the faces. These factors suggest that appraisal colors the amygdala response.
In a famous study, both Caucasian-American and African-American subjects showed greater amygdala activation when shown black faces than white faces. The authors suggest that their findings implicate cultural learning rather than innate values as the cause of this response. In other words, African-Americans are taught by the dominant group to fear members of their own in-group.
Once an individual becomes part of a group and adopts its values, it is notoriously dangerous for her to change her mind because the risk of social disapprobation feels daunting. Imaging studies shed light on brain regions that are activated when taking a risky position is contemplated. To simulate such risk, scientists often use simulated gambling tests in which subjects can take on different levels of risk while brain activity is measured. Sticking with the cards one is dealt with is a safe or default position, whereas trading in those cards for others is more risky. In a simulated gambling study, switching from the default option evokes activation of the anterior insula, a part of the brain associated with unpleasant emotions like disgust and fear. That is, moving away from a safe position is accompanied by danger warnings from a relatively primitive part of the human brain.
In the same gambling study, sticking with the default option is associated with activation of the ventral striatum. The brain’s “reward pathway” is often described as a dopaminergic pathway that includes the ventral striatum as a key component. The ventral striatum is involved in a process that allows us to associate social conformity with feelings of being rewarded. Hence, we learn to adhere strictly to the values of the group to which we belong, even when those values are biased, and to fear, often in a very primitive and instinctual manner, straying from the group.
Finally, subregions of the PFC are capable of suppressing activity in subcortical structures like the amygdala and the ventral striatum and thus is our greatest hope for reversing biased and even racist tendencies. The PFC is the most evolutionarily developed part of the human brain and among the functions that it serves are: reasoned appraisal, the ability to make judgments about people or situations based on evidence; response to instructions from others about how to approach tasks or situations; and the ability to recognize when we have been given erroneous information and to correct our ideas accordingly. Both preclinical and clinical studies show that engaging the PFC inhibits subcortical structures, like amygdala and insula, thus asserting reason over emotion.
It is probable that some of the propensity to affiliate with those most like us and shun those who seem different is genetically determined and innate. But the studies mentioned above strongly suggest that a lot of people’s biased tendencies are actually learned rather than innate. Some studies have shown that it is possible to reverse biased ideas through “counterbias” training, which involves pairing pictures with both biased and counter-biased words.
In one study, gender and racial biases were first measured by the Implicit Association Test, a study that quantifies unconscious bias. After that, subjects were trained to associate a specific tone with a picture and word pair that is incongruent with bias. For example, to reverse gender bias, subjects are shown pictures of females with both bias-incongruent words, like “math,” and bias-congruent words, like “painting,” but the tone was only presented when the word “math” appeared. A different tone was used for a pairing incongruent with racial bias. Then, while the subjects took a 90-minute nap, the tones were presented. Once awake, the IAT was administered again and the results showed that subjects who heard the specific tone for gender counterbias trials had reduced gender bias compared to baseline but not reduced racial bias. The opposite was the case for subjects who heard the tone specific for racial counterbias trials. By using a classical conditioning paradigm, implicit bias can be reduced.
In the case of understanding racial prejudice, brain imaging studies give us a firm basis to assert the learned aspect of this phenomenon. Studies using brain imaging and other neurobiological methods further suggest that learning that appeals to the PFC may hold unique promise for counteracting bias. Hopefully, this information will be used in studies that we urgently need to help us reverse the kind of devastating racial hatred and violence we recently witnessed in Charlottesville.
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 Hu X, Antony JW, Creery JD, Vargas IM, Bondenhausen GV, Paller KA: Unlearning implicit social biases during sleep. Science 2015;348:1013-1015