Psychopathic not psychotic. Normal people can sacrifice life much more easily when they have a degree of distance from the life because they don't have to empathize quite so much. Psychopaths don't really empathize, so they don't have that problem.

Psychopath.

There's a controversial, terrifying Dutch film that frames this issue pretty nicely.

http://en.wikipedia.org/wiki/The_Vanishing_(1988_film)

BTW, there is absolutely no fMRI study comprehensive enough that even remotely isolates psychopathy in the brain or satisfactorily describes its epidemiology.

It's all literally psychobabble from there. The idea that there might be a "psychopath gene" that is passed on in order to save us from great hardship, a kind of cold hard killer archetype to get us through times of great adversity, is an interesting one but there's just no hard evidence. It might just be "evil" that causes this stuff. It may as well be. We don't have the ability to figure it out right now.

Baleen might want to look into some of the work of Dr. James Fallon at UC Irvine.

I prefer the life-raft situation, because it's far more plausible:

Case 1: The life-raft can hold five people before it sinks. There are five people in the life raft, and one person in the water. Do you help the person into the life raft? Obviously not; one life is not worth five.

Case 2: The life-raft can hold five people before it sinks. There are currently six people in the life raft. Do you shove one person out of the life-raft before it sinks?

(Of course, the problem with the above is that, unlike the trolly problem, it's 'all or nothing')

You have two people oscillate in and out of the water to maintain the raft, you yourself should volunteer to be one of them.

This whole page is full of psychos in every situation presented and no they are not better at decision making.

"You have two people oscillate in and out of the water to maintain the raft"

Yeah well, what if the water's made of deadly acid, what then Mister Smartass?

Psychopaths can feel shame, at least in the sense that they are being mocked or disliked by others, so even if even ONE person knew of their dilemma (and would be able to say "hey! why the fuck didn't that guy do anything!") that would be motivation enough to act.

Because it can get them stuff they want?

That's a good point, but it still works against Dr. Quickbuck Popularizer's hypothesis. If what you say is true, a self-conscious psychopath would NOT push fatty off a bridge because a) she doesn't care about the people in the tram and b) norms would never criticize someone for not pushing an innocent man in front of a tram. In fact, they might feel a bit uneasy about someone who did push the fat guy, even though they'd have to acknowledge the utilitarian "correctness" of her actions.

Psychopaths can be moral, because psychopaths can be rational. You can train yourself, and be trained, to go beyond simple strategic considerations even if you don't have all the safety equipment. Further, a lot of popular ethoses are psychopath-compatible even without training -libertarianism and most religions, for example. They're shit ethoses though, of course.