The original paper is available at http://www.warwick.ac.uk/fac/soc/Economics/oswald/FinalJuly13Paris.pdf.
I think there's a major flaw in the experiment. When a subject pays to decrease the income of another subject, he's deciding to transfer some resources from himself and the other subject to the researchers (i.e. reduce the amount the researchers would pay out at the end of the experiment), and not to actually eliminate those resources. In order to show what the authors say the experiment shows, they should have made it clear to the subjects that paying to decrease another subject's income involves actual social loss. For example they could have committed to buying food with the money and then throwing them away in the garbage. I bet that would have made a huge difference.
