from pure self-interest, it makes sense to punish only if there is going to be a repeat game. it also makes sense to punish for altruistic reasons, or guided by “emotional” fairness reasons.

but personally, i would be mad not at the other player, but at the experimenters, for not giving me the chance to play the donor. why should i be the recipient ? was that choice made fairly ? and if it was (e.g. by a coin toss), then i would treat myself as the middle man while the other player won a lottery.. he would have to pay me commission to claim his money. as long as he paid me enough to make *me* happy, irrespective of what he is getting, i would let him claim his share. of course, $1 (out of $10) doesn’t cut it.. the outcome of the game would be different if played for a total of $10,000 of which he offered me $1000…