Psychology’s trolley problem might have a problem.

[...] For all this method’s enduring popularity, few have bothered to examine how it might relate to real-life moral judgments. Would your answers to a set of trolley hypotheticals correspond with what you’d do if, say, a deadly train were really coming down the tracks, and you really did have the means to change its course? In November 2016, though, Dries Bostyn, a graduate student in social psychology at the University of Ghent, ran what may have been the first-ever real-life version of a trolley-problem study in the lab. In place of railroad tracks and human victims, he used an electroschock machine and a colony of mice—and the question was no longer hypothetical: Would students press a button to zap a living, breathing mouse, so as to spare five other living, breathing mice from feeling pain?

“I think almost everyone within this field has considered running this experiment in real life, but for some reason no one ever got around to it,” Bostyn says. He published his own results last month: People’s thoughts about imaginary trolleys and other sacrificial hypotheticals did not predict their actions with the mice, he found.

It’s a discomfiting result, and one that seems—at least at first—to throw a boulder into the path of this research. Scientists have been using a set of cheap-and-easy mental probes (Would you hit the railroad switch?) to capture moral judgment. But if the answers to those questions don’t connect to real behavior, then where, exactly, have these trolley problems taken us?