I seem to remember reading - I forget where, sorry - that people with certain forms of brain damage were more likely to reason like consequentialists. Now it seems that our moral reasoning can even be affected by magnets.
Of course, this raises a host of interesting questions, some of which have already been picked up on over at Crooked Timber. It's not obvious what this shows about the correctness of our moral reasoning, if you believe in such a thing. I think that, like Amos Tversky and Daniel Kahneman's famous work on framing effects, it should encourage us to be wary about accepting our ordinary intuitions, knowing that they could vary on the basis of seemingly irrelevant factors. (Another example I heard in a recent talk was that experimental subjects made harsher moral judgements when disgusted by their surroundings - e.g. when there was half-eaten pizza left on the table.)