Teetering On The Footbridge

Imagine that you are the operator of a San Francisco cable car. One day, the car’s brakes go out, and you’re careering down Powell Street at an untoward speed. Ahead you see five students, crossing the track on their way home from class. There is no way to stop the car or warn the students. The only way to avoid killing all five is to throw a switch and turn onto another track. But if you do that you will run over and kill another student who is straggling behind the group. What do you do?

This is a slightly embellished version of what philosophers call the “trolley dilemma,” which is used to explore how people reason about morally ambiguous situations. The scenario is often used together with another, the so-called “footbridge dilemma.” In this case, a runaway trolley is again heading toward five innocent victims. But you’re no longer the driver. You and a fat man are standing on a footbridge overlooking the track, and you realize that the only way you can spare the five students is to push the fat man off the bridge, on to the track below. Push or no push?

Nevermind that even a very fat man would probably not stop a runaway trolley car. That’s not the point. Focus on the two dilemmas, which are fundamentally the same. In each, you can sacrifice one life to save five. Yet people react very differently to the two situations. People automatically see the logic in the trolley dilemma, and almost all opt for the utilitarian solution. But given the footbridge dilemma, most are morally repulsed by the idea of pushing the fat man off the bridge. They won’t do it. This seeming inconsistency has baffled both philosophers and psychologists for years.

Why does the human brain process these two dilemmas so differently? Why does our reason fail us on the footbridge? Northeastern University psychologists Piercarlo Valdesolo and David DeSteno are among the scientists who have been studying moral judgments in the laboratory, and they are coming to believe that moral reasoning is not as, well, reasonable as we like to think. Indeed, what we do in the name of morality may be more emotional than rational. According to the theory, humans operate according to certain “rules of thumb.” These are automatic, knee-jerk assessments, and they are very powerful, requiring a lot of mental work to overcome. Much of the time they are helpful, in routine everyday matters, but we also fall back on them in situations of uncertainty—or moral ambiguity. And they sometimes fool the more rational mind.

That’s what happens on the footbridge, say Valdesolo and DeSteno. Apparently one rule of thumb, emotionally powerful, says we don’t push people off bridges. Perhaps it’s the tactile nature of the act that makes it seem more like murder than saving lives. Whatever the source of the feeling, it’s strong enough to prevent what’s arguably the more reasonable (and moral) action: Keeping five students from perishing. There is experimental evidence for this: The rare few who do opt to sacrifice the fat man clearly struggle with the choice. They take much longer to decide, as if they had to free themselves from the tug of the quicker intuitive impulse.

Valdesolo and De Steno wondered: If our emotions are so influential in our moral judgments, might it be possible to determine people’s actions by manipulating their emotions? The short answer, as they report in the June issue of Psychological Science, is yes. The scientists presented research subjects with the two classical dilemmas, but before they did, they primed their emotions with completely irrelevant materials. One group watched a video clip of a Saturday Night Live skit, while another watched part of a short documentary about a Spanish village.

As funny as the Spanish village was, it was no competition for the Not-Ready-For-Prime-Time-Players, so the first group headed into the dilemmas feeling much more upbeat. And this uplifted mood trumped the negative feelings tied to the fat man falling. The participants were more likely to choose the practical, logical course of action on the footbridge, and what’s more, the longer they took the more likely they were to choose the greatest good for the greatest number. The mood manipulation did not affect choices in the trolley dilemma, which makes sense since this scenario was not as ambiguous to begin with.

None of this answers the fundamental question: Are you a better person if you murder one person to spare five? That’s for ascended masters. But you probably are a more humble person now, knowing just how easily your most profound judgments and actions can be shaped by others.

For more insights into human nature, visit the Association for Psychological Science website at www.psychologicalscience.org/onlyhuman.