Two groups of people — Mexican immigrants, and Muslims — have been the subject of much attention lately, and now researchers say they have figured out one psychological process that explains why some people in the United States vilify these groups.
The process, called dehumanization, occurs when people view others as less evolved and civilized than they view themselves, according to the study, which was published in January in the journal Personality and Social Psychology Bulletin.
But dehumanization may ultimately lead members of the targeted groups to have greater support for violent action, the researchers found in the study, which was conducted in the U.S. during the 2016 primary elections.
The new results show that the extent to which people in the U.S. dehumanize Mexican immigrants and Muslims "is very strongly correlated with support for then-candidate Donald Trump," study co-author Emile Bruneau, a neuroscientist at the University of Pennsylvania, told Live Science. In other words, the more a person "dehumanized" Mexican immigrants and Muslims, the more likely they were to support Trump. [Understanding the 10 Most Destructive Human Behaviors]
Nicholas Haslam, a professor of psychology at the University of Melbourne in Australia who was not involved in the study, said the study's methods and conclusions are sound. "It's high-quality, scrupulous work," he told Live Science. [5 Interesting Facts about Human Cooperation]
The study consisted of several experiments, two of which involved the popular "Ascent of Man" diagram, which illustrates the stages of human evolution, from the earliest human ancestor that looked a lot like an ape to the modern human. The people in the study were told to think of the diagram as a scale, with the ape-like human ancestor as 0 and the modern human as 100.
In one experiment, the researchers asked 342 non-Hispanic Americans where they would place Mexican immigrants and non-Hispanic Americans on the Ascent of Man scale. In another experiment, the researchers asked 455 non-Muslim Americans to place Muslims and non-Muslim Americans on the same evolutionary scale.
The researchers found that some of the people placed both Mexican immigrants and Muslims lower on the scale (meaning farther away from the modern man) compared with their placement of non-Hispanic or non-Muslim Americans, respectively.
The researchers also asked the participants which presidential candidate they supported. They found that the people who supported Trump were more likely to dehumanize Mexican immigrants and Muslims, compared with those who supported any of the other Democratic or Republican candidates.
In other parts of the study, the researchers looked at how the perception of being dehumanized might affect Mexican immigrants and Muslims. The participants in this part of the study included 283 Mexican immigrants and 124 Muslims.
Mexican immigrants who said they felt dehumanized by Trump were also more likely to dehumanize Trump and support anti-Trump initiatives, such as boycotting his businesses, compared with those who did not feel dehumanized by Trump, the researchers found. In addition, those individuals who felt dehumanized by Trump were more likely to "want to see him personally suffer, and endorse hostile actions such as spitting in his face," according to the study. [6 Politicians Who Got the Science Wrong]
Furthermore, Muslims who said they felt dehumanized by non-Muslim Americans were more likely to support violent approaches to supporting civil rights for Muslims in the U.S. compared with supporting nonviolent approaches, the researchers found.
The results show that dehumanizing Muslims and Mexican immigrants in the first place may help to establish, and fuel, a vicious cycle of dehumanization, the researchers said.
"If we use rhetoric and enact policies that make Muslims feel dehumanized, this may lead them to support exactly the types of aggression that reinforce the perception that they are 'less civilized' than 'us,'" Bruneau said in a statement. "In this way, dehumanization can become self-fulfilling in the minds of the dehumanizers and justify their aggression."
The researchers noted that there were some limitations to the study, including the fact that the researchers were not able to establish a cause-and-effect relationship between certain factors in the study based on the data. For example, although the researchers found that some people's tendency to dehumanize Mexican immigrants and Muslims was strongly linked to those people's support for Trump, the findings do not prove that those people supported Trump because of their tendency to dehumanize these groups. However, it is possible that people support Trump not despite this rhetoric, "but in part because of it," the researchers wrote.
Originally published on Live Science.