[ahenchan]

I have not read the original paper, but it seems plausible that the experimenters would have tried different game rules and this is the version which gives the reported result most strongly. On that assumption, one way to look at the experiment is as a test of the limits of rational behaviour. The 'vengeful chump' might be interpreted as externalising their embarrassment at having failed to identify the optimum strategy. Unconsciously they know they should have cheated, but it is more gratifying to blame someone else. I'd like to read the entire paper if anyone can please show where it can be got (for free natch).