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Would you kill one person to let five live?

Would you kill someone? Actually, let's clarify the question: Would you kill someone if doing so was the only way to save the lives of five other people? A new study conducted by researchers at Michigan State University suggests you probably would.

The so-called "trolley problem" is a classic dilemma in moral philosophy. Here's the basic set up: A trolley is running out of control and is heading toward five people tied to the track. You are operating the trolley, and can choose to flip a switch that would divert it to another track, where, unfortunately, a single person is tied down. Do you choose to flip the switch or do nothing?

Undergraduates have been debating the problem for decades. Utilitarians – those who maintain that it's the consequences of an act that count and that people should act to maximize the greater good –would argue it's morally permissible to flip the switch. Until now, however, the thought experiment has been kept the classroom.

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But researchers have put it to the test, in a study published in the journal Emotion.

Study participants were put in a three-dimensional simulator that put them behind the wheel. A vast majority of them – 90 per cent – chose to pull the switch.

"What we found is that the rule of 'Thou shalt not kill' can be overcome by considerations of the greater good," evolutionary psychologist Carlos David Navarrete, lead researcher on the project, said in a release.

This is the first time the dilemma has been posed as a behaviour experiment in a virtual environment, "with the sights, sounds and consequences of our actions thrown into stark relief," the study says.

With sensors attached to their fingertips to monitor emotional arousal, 133 of the 147 participants opted to steer the boxcar away from the five people and toward a single individual. Only 14 people allowed the boxcar to kill the larger group. Of those 14, three initially pulled the switch but then returned it to its original position.

Those who could not bring themselves to pull the switch were found to be more emotionally aroused, perhaps because of the heightened anxiety of the situation.

"I think humans have an aversion to harming others that needs to be overridden by something," Dr. Navarrete said. "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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Or maybe they're just Kantians (inside philosophical joke – hey-oh!).

What would you do? Flip the switch or keep the trolley on its course?

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About the Author

Dave McGinn writes about fitness trends for the Life section and also reports for Globe Arts. Prior to joining the Globe, he was a freelance journalist, covering topics from trying to eat Michael Phelps' diet to why the Joker is the best villain in comics history. He's working on improving his 10k time. More

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