Would you kill 1 person to save 5 others?

MICHIGAN STATE (US) —A new study suggests a vast majority of people are willing to violate a moral rule if it means minimizing harm, in this case letting one person die to save five others.

For the study published in the journal Emotion, participants watched a three-dimensional scene in which a runaway boxcar was heading toward five people who could not escape its path. The study participants were given the power to reroute the car to another track with only one person along the route. Ninety percent of them threw the switch.

“What we found is that the rule of ‘Thou shalt not kill’ can be overcome by considerations of the greater good,” says Carlos David Navarrete, an evolutionary psychologist at Michigan State University and lead researcher on the project.

Participants wore a head-mounted device that presented them with a 3-D simulated version of the boxcar scenario. (Credit: Michigan State University)


The experiment offers a new twist on the “trolley problem,” a moral dilemma that philosophers have contemplated for decades. But this is the first time the dilemma has been posed as a behavioral experiment in a virtual environment, “with the sights, sounds, and consequences of our actions thrown into stark relief,” according to the study.

The participants were presented with a 3-D simulated version of the dilemma though a head-mounted device. Sensors were attached to their fingertips to monitor emotional arousal.

In the virtual world, each participant was stationed at a railroad switch where two sets of tracks veered off. Up ahead and to their right, five people hiked along the tracks in a steep ravine that prevented escape. On the opposite side, a single person hiked along in the same setting.

As the boxcar approached over the horizon, the participants could either do nothing—letting the coal-filled boxcar go along its route and kill the five hikers—or pull a switch (in this case a joystick) and reroute it to the tracks occupied by the single hiker.

Of the 147 participants, 133—90.5 percent—pulled the switch to divert the boxcar, resulting in the death of the one hiker. Fourteen participants allowed the boxcar to kill the five hikers (11 participants did not pull the switch, while three pulled the switch but then returned it to its original position).

The findings are consistent with past research that was not virtual-based, Navarrete says.

Participants who did not pull the switch were also more emotionally aroused. The reasons for this are unknown, although it may be because people freeze up during highly anxious moments—akin to a solider failing to fire his weapon in battle.

“I think humans have an aversion to harming others that needs to be overridden by something,” Navarrete says. “By rational thinking we can sometimes override it—by thinking about the people we will save, for example. But for some people, that increase in anxiety may be so overpowering that they don’t make the utilitarian choice, the choice for the greater good.”

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