If you have trouble understanding people you disagree with about immigration, perhaps you can blame it on a weak stomach.
In a study that adds to a growing body of research about the influence that unconscious emotions exert on political thought, researchers at Aarhus University in Denmark found a link between heightened sensitivity to disgust and an aversion to interacting with immigrants.
The study highlights the challenges faced by political opponents in using facts and reason to find a common ground on social issues. The scientists show how a primeval fear of infection, forged long ago in humanity's evolutionary past, can give rise to a modern-day aversion to interacting with immigrants. This is by no means true for everybody, but that fear can make it more difficult, but by no means impossible, for some people to willingly interact with immigrants.
"Individuals with high disgust sensitivity are especially motivated to avoid contact with immigrants," says lead author Lene Aarøe, a professor of political science at Aarhus University in Denmark. "This is important because avoiding contact potentially prevents the kind experiences that typically stimulate tolerance."
Professor Aarøe and her colleagues showed participants images related to infection and disease and measured their the flight-or-flight responses via skin conductance, as reported in a paper published Monday in the American Political Science Review.
The researchers found that subjects with the strongest response to the images were also those most likely to say that they would disapprove if someone in their immediate family were to marry an immigrant or if immigrant families moved into their neighborhoods. Overall, they were less willing to eat food prepared by immigrants or to share public spaces with immigrants.
Surprisingly, the heightened disgust response was far more likely to predict such aversion to interacting with immigrants than did income, education, or even political ideology.
"When we saw these data patterns we knew that we were onto something," says Aarhus University political scientist Michael Bang Petersen, who co-authored the paper. And not just something that was academically interesting but something with real-world consequences for the integration of immigrants into society."
Researchers have found similar correlations between heightened disgust responses to conservative political views, including opposition to same-sex marriage and prejudicial attitudes toward gays and lesbians.
In some cases, these variations can translate into drastic policy prescriptions, particularly when it comes to people from foreign places. "People with sensitive behavioral immune systems shun any situation that brings them closer to immigrants and favor situations that limits contact, such as the creation of ghettos," Dr. Petersen says. "In fact, it seems like people with sensitive behavioral immune systems prefer something that could be construed as apartheid-like arrangements."
Politicians and pundits are adept at leveraging disgust responsiveness to sway people to support their policies. Donald Trump – who describes himself as a "germaphobe" and has called the practice of shaking hands "barbaric" – said in 2015 that "tremendous infectious disease is pouring across the border" from Mexico to the United States, a claim that the fact-checking website Politifact, after checking with health experts, deemed "unlikely."
His words echoed those of television personality Lou Dobbs, who in 2007 drew criticism for falsely claiming that undocumented immigrants were importing an epidemic of leprosy.
"Immigrants are not a source of infection," says Aarøe. "It is on the subconscious level that the immune system misinterprets differences as a potential sign of infection."
The tendency for disgust and associated emotions to operate outside of our conscious awareness can make our political positions, particularly on social issues, more resistant to facts.
"Politics is at least as much about emotionality as it is about rationality," says Kevin Smith, a political scientist at the University of Nebraska in Lincoln. "It clearly seems to be that people literally – not metaphorically, literally – experience the world differently because they have these variations in these systems that gather and translate information about the environment they're in."
Knowing that different people are born with different emotional systems might even foster patience for political differences. "There is a divide between conservatives and liberals," says Patrick Stewart, a political scientist at the University of Arkansas who has also tested disgust responses and their relationship with political ideology. "It's not because one or the other is bad. It just might be that they're adapted to deal with different environments."
The researchers hope that their work can help free us of the influence that unexamined emotions can exert on our political attitudes. "One way to enable people to correct for their psychological biases is to inform them about them," says Aarøe.
And while different people may have different levels of disgust sensitivity, scientists agree that we are always capable of changing our own minds.
"If you actually put a little bit of mental work and examine why you don't like immigration policy, and you weigh the pros and cons rationally you can certainly think your way to a different position," says Smith. "We're not talking about predestination, we're really talking about predisposition."