It seems to me that Yvain keeping money which he himself arranged to give away should not necessarily be considered to have positive utility. That leaves self-interest. But whether self-interest can/should motivate cooperation is the fundamental question of PD in the first place, isn’t it?
I assume the 60 dollars still has value to Yvain even though he was willing to spend some fraction of it. I don’t see any reason to assume this money is less valuable to Yvain than to the generic survey taker.
It seems to me that Yvain keeping money which he himself arranged to give away should not necessarily be considered to have positive utility. That leaves self-interest. But whether self-interest can/should motivate cooperation is the fundamental question of PD in the first place, isn’t it?
I assume the 60 dollars still has value to Yvain even though he was willing to spend some fraction of it. I don’t see any reason to assume this money is less valuable to Yvain than to the generic survey taker.