Monday, February 27, 2012

Pushing people off bridges, and consequences.

Pushing people off of bridges - but only to save the lives of others, of course - has long been one of the staples of debate in moral philosophy.  The original formulation of the famous Trolly Problem is more or less "Suppose you see an out of control trolley about to run over 5 people.  Is it moral to push a fat person under the wheels if it means that only he will die instead of the 5 others."  This started out as a debate among philosophers, then became a tool for cognitive scientists to use by asking people about this topic in surveys, but often with some variation.  What if the one person is your mother?  What if you throw a switch instead of having to push the person yourself?

Researchers have found out many fascinating things about how people respond to moral problems, or at least say they would respond, using this problem.  I'll plug Thinking Fast and Slow here as an excellent overview of modern cognition research in a lot of areas, including this one.  Strangely for people who try to describe morality in terms of simple abstract rules, almost everyone would throw a switch to divert the trolley from hitting five people to a course that would make it hit only one, while very few would actually push someone themselves.

I'd tend to explain that with two forces.  First, in real life I can be much more certain that pushing someone will result in harm than I can be that, further down the track, the train will cause harm by itself.  It could be diverted by someone else, I could be wrong about where it was going, etc.  Second, there is the notion of blame.  I wasn't to blame for the out of control train so I can't be blamed for the five deaths, but if I push someone onto the tracks I'm now the proximate cause of them dying.  In matters of abstract morality you can talk about partial responsibility, but in terms of lynch mobs usually its just a matter of finding the one person who is "to blame".

However, I recently read a blog post discussing the finding that people are much more likely to push if all the participants are related than if they are strangers, going from about a quarter to about half.  The blog post author, Robin Hanson, suggests that being related makes the stakes higher, enough so that more people are willing to violate social norms.

That's possible, but I think a stronger consideration would be that in the case of strangers the relatives of the person you killed are mostly disjoint from the people whose relative you save, while in the case of the brothers most of the people most upset by the killing will also be most relieved by the other results.  I'd suggest running a new experiment, where the person pushed and the five on the tracks are all related to each other but not to the person answering the question.  My bet would be that closer to half than to a quarter would end up saying that they would push.

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