Summary: Researchers suggest our neural circuits help explain why we feel comfortable around those who resemble us and why we often feel uneasy around people who differ from us.
Source: The Conversation.
Anti-immigrant policies, race-related protests, Title IX disputes, affirmative action court cases, same-sex marriage debates.
These topics frequently dominate the news. Even thoughtful analyses often fall back on framing them as clashes between opposing groups: Black versus white, women versus men, gay versus straight. At a basic biological level, organisms benefit from distinguishing between species. But within our own species, might neural circuitry also incline us toward preferring those like us and feeling wary of those who are different?
Brain battle between distrust and reward
Human brains, like those of other animals, balance two ancient systems. One involves the amygdala, a brain region that can trigger fear and distrust in response to perceived threats—whether predators or unfamiliar places. The other involves the mesolimbic system, a network that drives feelings of pleasure and reward that support survival—anything from food to social rewards like trust.
How do these systems shape our sense of community and our reactions to people who are different from us?
Implicit association tests reveal the strength of unconscious associations. Many people show an implicit preference for their own group—an in-group—even when they do not express explicit bias. For example, studies have found that white participants can implicitly associate Black people with violence and threat, and this unconscious bias can appear even in perceptions of Black boys as young as five.
Brain imaging reveals increased amygdala activity when people make split-second judgments about the trustworthiness of faces. These rapid responses occur too quickly to reflect conscious deliberation and likely reveal implicit fears. Experimental priming can worsen this effect: in one study, playing violent rap music to white participants increased amygdala activation and made it harder for cortical executive regions to suppress that implicit bias. Normally, higher-order cortical areas can override the amygdala’s quick push toward distrust when we encounter out-group members.
Research is nuanced and must distinguish explicit from implicit measures, as well as account for cultural and individual differences. Still, converging evidence suggests that amygdala signaling contributes to reluctance to trust others and to in-group versus out-group preferences. Much of the instinct to distrust “others” can be traced to neural circuitry involved in fear and anxiety.
Reward from ‘sameness’
By contrast, mesolimbic circuits mediate reward. These pathways include dopamine-releasing neurons associated with pleasure and reinforcement. Dopamine in these circuits underlies the rewarding aspects of many behaviors and can be linked to addictive behaviors, from substance use to problematic gaming and gambling.
Other neurochemicals, such as oxytocin, can modulate mesolimbic circuits and alter our sense of social reward. Oxytocin and related signaling can increase feelings of trust and bonding, enhancing the reward value of social interactions.
Methodological differences across studies mean more research is needed to map precisely how these signaling pathways function in humans during in-group versus out-group encounters. Nevertheless, comparative studies in other mammals offer useful clues because social reward and fear circuits are evolutionarily ancient and present across vertebrates.
Groundbreaking animal work has provided mechanistic insight. For example, researchers using fiber photometry and genetic tools in mice have been able to monitor and manipulate specific dopamine neurons while mice interacted socially. These studies showed that certain dopamine neurons in the mesolimbic system become particularly active when a mouse meets a novel mouse of the same genetic line—suggesting a neural reward response to “sameness.”
By contrast, encounters with mice of a different genetic line or with other species that have distinct social structures might engage fear-related circuits more strongly. Studies of voles, which vary in social organization depending on species and environment, illustrate that social context and species-specific behavior interact with neural signaling to shape social responses.
Although scientists are still uncovering how subtle differences influence neural circuits across species, animal models help illuminate how human brain systems might contribute to implicit, unconscious biases toward those who differ within our own species.
Neural signaling is not destiny
Even if evolution has biased the brain to reward similarity and to be wary of difference, this is not unchangeable fate. Brain activity is plastic: higher-order cortical regions can modulate primitive fear and reward systems to produce more flexible behavior.
Author Chimamanda Ngozi Adichie has argued that “the problem with stereotypes is not that they are untrue, but that they are incomplete. They make one story become the only story.” Stereotypes reduce people to their differences and omit fuller, richer perspectives.
Why tolerate the discomfort differences provoke rather than always choosing the immediate reward of sameness? Social scientist Scott Page argues, with mathematical and historical examples, that diverse groups—though less predisposed to trust one another initially—produce better solutions when they work together. From codebreaking during World War II to modern problem solving, a range of perspectives often outperforms a homogenous group of experts.
In short, diversity can trump pure ability by generating greater innovation and more effective solutions. Recognize the amygdala’s role in fostering distrust when we encounter difference, but also acknowledge the distinct, longer-term rewards of working with people unlike ourselves. Those rewards—improved creativity, problem solving, and collective success—offer powerful reasons to move beyond instinctual discomfort.
Funding: Leslie Henderson has received funding from the National Institutes of Health.
Source: Leslie Henderson – The Conversation
Publisher: Organized by NeuroscienceNews.com
Image Source: Images adapted from The Conversation news release.
The Conversation (2018, June 25). Why Our Brains See the World As “Us” Versus “Them”. NeuroscienceNews. Retrieved June 25, 2018.