How Implicit Bias Works, According to Neuroscience

Optical illusions occur when our brains misinterpret something that our eyes see. They are a type of mindbug—an error that our brains make when processing and responding to information. Another type of mindbug is implicit bias: prejudice we hold without being consciously aware of it, often misaligned with our consciously held beliefs. Everyone has implicit biases, which developed evolutionarily as a survival tactic to help humans quickly identify whether someone could be a threat or an ally. However, implicit biases today can build prejudice and systemic inequality that lead to the mistreatment and discrimination of others based on factors like race, gender, sexual orientation, socioeconomic status, abilities, language, or age.

While the beliefs held by the subconscious may seem abstract, implicit bias has been studied extensively by neuroscientists. Starting as a survival mechanism, the human brain evolved the ability to differentiate between those who are similar to oneself and those who are considered “other.” The medial prefrontal cortex (serving as the command center for emotional regulation and social cognition) is part of this mechanism, with the ventromedial prefrontal cortex that responds to stimuli considered related to the individual and the dorsomedial prefrontal cortex that responds to stimuli that are considered to relate to others. Consequently, the ventromedial prefrontal cortex activates when a person is perceived as being in the same group as you, while the dorsomedial prefrontal cortex activates when the brain perceives someone as “other.” 

By dividing people into groups, the brain assigns stereotypes to them, which not only influence how we think but also translate into our interactions with others. This occurs through the activation of mirror neurons, neurons linked to empathy by causing us to “mirror” the emotions of the people around us. This is known as emotional contagion, which is when we feel the emotions we perceive others to be experiencing in response to their physical cues, informing how we interact and connect with them. When interacting with people who are considered similar, mirror neurons experience greater activation, leading to increased empathy and interest. By contrast, mirror neurons are less activated when interacting with someone considered “other,” leading to decreased empathy for and interest in them.

There are different factors that can exacerbate implicit bias. For example, it can become stronger when one is tired and stressed. This is because relying on stereotypes bears less of a cognitive load than making conscious, individualized judgments about people. This is essentially the brain taking shortcuts, similar to it being tricked by optical illusions. These shortcuts begin developing as early as infancy, when young children observe and form preferences for the characteristics of the people who are familiar to them. In fact, one of the major ways babies begin to learn about the world is through the actions of the adults around them. Adults can show children who they should assign value to and who should be considered trustworthy, intelligent, or safe based on race, gender, or other factors. They can do so even without realizing it through their actions, as the way that adults treat others demonstrates to children how they should treat others. This can lead to implicit biases being passed on. These implicit biases are solidified over time through confirmation bias, where observations and experiences are perceived as confirming expectations.

Because this phenomenon initially developed as a survival mechanism, it is closely related to the brain’s fight-or-flight response, regulated by the amygdala, a part of the limbic system, which controls behaviors and emotions related to survival. The amygdala triggers processes that cause elevated heart and breathing rates and redirect where blood and oxygen are sent in the body in an attempt to ensure survival in response to fear. A fear response occurs through the amygdala before the prefrontal cortex, the part of the brain responsible for making rational decisions, is able to make conscious judgments that may be different from the automatic, biased response. Implicit bias can lead the amygdala to activate for different reasons, including the perception of danger based on stereotypes or the social threat of being judged for being biased. The sensitivity with which the amygdala is activated is largely determined by the influences of adults and one’s surroundings during childhood. An example of this is the observed correlation between children interacting more with people of different races and having lower rates of activation of the amygdala when doing so later in life.

Such observations can be made with technology that is used to scan the brain or measure its electrical activity. Event-related brain potentials (ERPs), for example, have been used broadly in neuroscience since the mid-20th century, measuring electrical activity at the scalp as the brain processes information about the people it observes in real time. These ERPs have demonstrated that the average person is able to process information about someone’s perceived race and gender, along with their emotional state and age, within 200 milliseconds of seeing them. The areas of the brain involved in this information processing have been shown using functional magnetic resonance imaging (fMRI), which shows blood flow in the brain and how it changes in response to observing people perceived as being in different groups.

One of the most severe consequences of implicit bias is structural inequality—unequal treatment and access to opportunity on a systemic level. This can be particularly dangerous in areas such as criminal justice and health care, where lives are at stake. The effects of implicit bias on criminal justice were demonstrated by the University of Chicago’s Shoot/No Shoot test, in which participants were shown images of African American and Caucasian men holding cans of soda, cell phones, or guns and were told to press a computer key indicating that the man would be shot if they believed the item he was holding was a gun. The test found that participants were more likely to indicate that they believed the African American men should be shot despite the fact that more African American men were holding cans of soda or cell phones. It also took participants a greater amount of time to determine that the African American men were holding harmless objects compared to the time it took them to make the same decision about the Caucasian men. The results of this experiment reveal the larger societal bias of associating African Americans with crime and danger, which is reflected in the disproportionate incarceration of and police brutality toward African Americans and other people of color. Implicit bias can also lead to health care providers having unconscious preferences for some patients and providing lower-quality care to others, particularly negatively affecting people of color, women, members of the LGBTQIA+ community, the elderly, people with obesity, people with disabilities, people with less education, and people of lower socioeconomic status. The overlap of these identities means that people can experience biases against them on multiple levels, leading to multiple factors shaping the treatment they receive, a concept known as intersectionality.

Ultimately, the ability to explain implicit bias using neuroscience does not mean that implicit bias should be normalized. Instead, it enables us to understand implicit bias and therefore empowers us to fight it. It is not enough for us to say that we consciously believe in justice and equity and therefore our implicit biases don’t matter; if we truly care about justice and equity, we must actively challenge our implicit biases. In order to do so, it is necessary to accept that we all have implicit bias and to practice mindful reflection to uncover our own specific biases, questioning why we make the judgments we do about people and how those judgments shape our interactions with them. It is also important to educate ourselves so that we are better informed and can challenge stereotypes. We can challenge stereotypes by limiting the assumptions we make about others based on the social groups we perceive them as being in, instead recognizing them as individuals. By confronting our implicit biases, we are able to claim greater authority over our minds and are empowered to fight not only against the biases within our brains but also for a more just society that does not accept the inequities that these biases create.