|Fat men are actually harder to push to their deaths than philosophers assume|
In 1999, Joshua Greene—then a philosophy graduate student at Princeton, now a psychology professor at Harvard—had a very fertile idea. He took a pretty well-known philosophical thought experiment and infused it with technology in a way that turned it into a very well-known philosophical thought experiment—easily the best-known, most-pondered such mental exercise of our time. In the process, he raised doubts, in inescapably vivid form, about the rationality of human moral judgment.
The thought experiment—called the trolley problem—has over the past few years gotten enough attention to be approaching “needs no introduction” status. But it’s not quite there, so: An out-of-control trolley is headed for five people who will surely die unless you pull a lever that diverts it onto a track where it will instead kill one person. Would you—should you—pull the lever?
Now rewind the tape and suppose that you could avert the five deaths not by pulling a lever, but by pushing a very large man off a footbridge and onto the track, where his body would slow the train to a halt just in time to save everyone—except, of course, him. Would you do that? And, if you say yes the first time and no the second (as many people do), what’s your rationale? Isn’t it a one-for-five swap either way?
Greene’s inspiration was to do brain scans of people while they thought about the trolley problem. The results suggested that people who refused to save five lives by pushing an innocent bystander to his death were swayed by emotional parts of their brains, whereas people who chose the more utilitarian solution—keep as many people alive as possible—showed more activity in parts of the brain associated with logical thought.
If you put Greene’s findings in general form—human “reasoning” is sometimes more about gut feeling than about logic—they are part of a wave of behavioral-science research that in recent years has raised doubts about how much trust your brain deserves. The best-seller lists have featured such books as Predictably Irrational, by the Duke psychologist Dan Ariely, and Thinking, Fast and Slow, in which the Princeton psychologist and Nobel laureate Daniel Kahneman covers acres of research into humanity’s logical ineptitude.
Presumably, the question comes with some explanation for why only somebody fatter than yourself will do the trick? But, how do you know? In what universe do runaway trolleys come with a safety label that reads: "Your 197 pounds is not heavy enough. Only an NFL offensive lineman-sized fat man will do."
So maybe the aversion to pushing fat men to their deaths of most people who aren't utilitarian philosophers makes a little sense?