If you had the option of saving five lives by pushing one person into an oncoming train, what would you do?
If asked this question in your native language, you’d likely refuse to make the shove, studies have shown. But if the question was posed in a foreign tongue, you’d more easily conclude that five lives are worth more than one—and choose to push someone to their death.
Now scientists think they can explain this distinction. New research from the University of Chicago, published in the journal Cognition (paywall), suggests that our relationship to a language influences the mental imagery that our brains produce in response, and foreign languages give rise to less vivid mental imagery. “The languages we use are not simply interchangeable vehicles for transmitting ideas,” cognitive psychologist Sayuri Hayakawa, who co-authored the study, tells Quartz. “Rather, the language itself can change how we think and feel about those ideas.”
Hayakawa and his colleague Boaz Keysar devised three tests to examine the link between language, vividness of mental imagery, and moral choices. In the first, about 350 subjects were asked about the vividness of imagery that arose in their minds when discussing sensory experiences like sight and touch. English speakers produced less clear mental pictures when hearing sense words in Spanish than their native tongue.
The next test had participants judge shapes in order to examine the link between muted mental imagery and accuracy, using 300 Mandarin Chinese speakers living in Beijing, who spoke English. In one variation of a series of exercises, they were given certain words—for example, “pen,” “carrot,” and “mushroom”—then asked to choose which was shaped most differently from the other two. In this case, the answer was the mushroom. They were also asked which shape didn’t fit in the category based on meaning, which was the pen. For the subjects, taking the test in their native language produced more vivid pictures. When a clear mental image was produced, subjects could respond correctly. However, muted pictures made correct judgment more difficult. In English, the subjects didn’t see as vividly.
The third test tied muted mental imagery to moral choices. Previously, the researchers had found that people were up to twice as likely to make a utilitarian choice—sacrificing one life to save five—when asked in a foreign tongue as opposed to their native language. Since then, the finding has been independently replicated with hundreds of speakers of English, Korean, Spanish, French, Hebrew, German, and Italian.
This time, the researcher wanted to determine the relationship between the language spoken, the vividness of mental images produced, and the moral decision made.
Over 700 German speakers were asked to consider the moral dilemma of saving five lives by sacrificing one. The subjects didn’t grow up speaking English at home. On average they’d begun learning it at age 14, and had spent about 3 months abroad in an English-speaking country.
The group was randomly split in half, and asked to consider the problem in one of the two tongues, English or German. They rated their decisions on a scale of 1-7, with 1 being vehemently opposed to sacrificing a life, and 7 indicating absolute certainty that saving five lives is right. They also rated the vividness of the mental picture of the scene, the potential sacrificial victim, and the five people who could be saved on a 1-7 scale from “no image” to “absolutely clear image.”
Notably, vivid imagery of the individual to be sacrificed, even when produced in a foreign language, influenced the outcome of the subjects’ moral decision-making. So some speakers—about 7% of native German speakers being asked the question in English—could really see the individual involved, even when the rest of the scene was hazier, and that affected their choice. In other words, being able to clearly visualize who would pay the price for the choice made a difference in the decisions. But ultimately, native German speakers generally couldn’t see the scene, the individual, or the five people whose lives could be saved as clearly when listening to a description in English.
The three tests taken together “suggest that our mental images change when using a foreign tongue, leading to downstream consequences for how we make decisions,” the researchers write.
Hayakawa explained to Quartz how this works. When a scene is described in your native language, those words are intimately linked to a rich store of memories and associations, which help build a vivid image of what you’re hearing. But foreign languages won’t elicit as clear imagery because they’re less often associated with deep formative experiences.
If you’re an English speaker who took French in school, when you listen to a scene described in French, you understand the words. But their linguistic gravitas will be less weighty than a description in your first language, and the mental imagery your brain produces won’t be as clear or meaningful. The weight words have, which creates a more or less vivid picture in your mind, will shift depending on the tongue spoken. “As a result,” Hayakawa says, “the way you feel about and act on my words can vary depending on what language I choose to deliver the message.”
Familiarity with a language is, of course, not the only factor in our response to words at any given time. The weather, health, and happiness also influence responses, according to Hayakawa. Still, it’s worth noting the effect of words on the mind and the images we produce, because they can have a hidden influence on our choices.
“These findings speak to the complex and highly interconnected processes involved in seemingly simple acts. When I ask you to ‘imagine pushing a man off of a bridge,’ this involves unpacking the meaning of what I am saying, retrieving the appropriate exemplars from memory to build your mental picture, and reflecting and emotionally responding to this image,” Hayakawa says. “Using a foreign language could potentially influence how you carry out any of these steps, from the comprehension of the message to the construction of the image.”
Read next: You now see colors that once didn’t exist