If you could save the lives of five people by pushing another bystander in front of a train to his death, would you do it? And should it make any difference if that choice is presented in a language you speak, but isn’t your native tongue?

Psychologists at the University of Chicago found in past research that people facing such a dilemma while communicating in a foreign language are far more willing to sacrifice the bystander than those using their native tongue. In a paper published Aug. 14 in Psychological Science, the UChicago researchers take a major step toward understanding why that happens.

“Until now, we and others have described how using a foreign language affects the way that we think,” said Boaz Keysar, the UChicago psychology professor in whose lab the research was conducted. “We always had explanations, but they were not tested directly. This is really the first paper that explains why, with evidence.”

Through a series of experiments, Keysar and his colleagues explore whether the decision people make in the train dilemma is due to a reduction in the emotional aversion to breaking an ingrained taboo, an increase in deliberation thought to be associated with a utilitarian sense of maximizing the greater good or some combination of the two.

“We discovered that people using a foreign language were not any more concerned with maximizing the greater good,” said lead author Sayuri Hayakawa, a UChicago doctoral student in psychology. “But rather, were less averse to violating the taboos that can interfere with making utility-maximizing choices.”

The researchers, including Albert Costa and Joanna Corey from Pompeu Fabra University in Barcelona, propose that using a foreign language gives people some emotional distance and that allowed them to take the more utilitarian action.

“I thought it was very surprising,” Keysar said. “My prediction was that we’d find that the difference is in how much they care about the common good. But it’s not that at all.”

Studies from around the world suggest that using a foreign language makes people more utilitarian. Speaking a foreign language slows you down and requires that you concentrate to understand. Scientists have hypothesized that the result is a more deliberative frame of mind that makes the utilitarian benefit of saving five lives outweigh the aversion to pushing a man to his death.

But Keysar’s own experience speaking a foreign language—English—gave him the sense that emotion was important. English just didn’t have the visceral resonance for him as his native Hebrew. It wasn’t as intimately connected to emotion, a feeling shared by many bilingual people and corroborated by numerous lab studies.

“Your native language is acquired from your family, from your friends, from television,” Hayakawa said. “It becomes infused with all these emotions.”

Foreign languages are often learned later in life in classrooms, and may not activate feelings, including aversive feelings, as strongly.

The problem is that either the “more utilitarian” or the “less emotional” process would produce the same behavior. To help figure out which was actually responsible, the psychologists worked with David Tannenbaum, a postdoctoral research fellow at the University of Chicago Booth School of Business at the time of the research and now an assistant professor at the University of Utah.

Tannenbaum is an expert at a technique called process dissociation, which allows researchers to tease out and measure the relative importance of different factors in a decision process. For the paper, the researchers did six separate studies with six different groups, including native speakers of English, German and Spanish. Each also spoke one of the other languages, so that all possible combinations were equally represented. Each person was randomly assigned to use either his or her native language or second language throughout the experiment.

Participants read an array of paired scenarios that varied systematically in key ways. For example, instead of killing a man to save five people from death, they might be asked if they would kill him to save five people from minor injuries. The taboo act of killing the man is the same, but the consequences vary.

“If you have enough of these paired scenarios, you can start gauging what are the factors that people are paying attention to,” Hayakawa said. “We found that people using a foreign language were not paying any more attention to the lives saved, but definitely were less averse to breaking these kinds of rules. So if you ask the classic question, ‘Is it the head or the heart?’ It seems that the foreign language gets to the heart.”

The researchers are next looking at why that is. Does using a foreign language blunt people’s mental visualization of the consequences of their actions, contributing to their increased willingness to make the sacrifice? And do they create less mental imagery because of differences in how foreign language use affects which memories come to mind?

The researchers are also starting to investigate whether their lab results apply in real-world situations where the stakes are high. A study Keysar’s team is initiating in Israel looks at whether the parties in a peace negotiation assess the same proposal differently if they see it in their own language or the language of their negotiating partner. And Keysar is interested in looking at whether language can be usefully considered in decisions made by doctors speaking a foreign language.

“You might be able to predict differences in medical decision-making depending on the language that you use,” he said. “In some cases you might prefer a stronger emotional engagement, in some you might not.”

Citation: “Thinking More or Feeling Less? Explaining the Foreign-Language Effect on Moral Judgment,” Sayuri Hayakawa, David Tannenbaum, Albert Costa, Joanna D. Corey and Boaz Keysar, Psychological Science, Aug. 14, 2017. DOI: 10.1177/0956797617720944

Funding: John Templeton Foundation, National Science Foundation, Spanish Government, Ministry of Economy and Competitiveness, Catalan Government, European Research Council and University of Chicago.