Also, I wonder if you’d reconsider the use of the words “insane” and “crazy” to mean “irrational.” Aversion to inequality in the ultimatum game follows its own logic in the context of interactions in which social norms dictate that a decision maker should punish/discourage selfish behavior for the benefit of others in a social group, and ultimately, the decision maker. Since inequality aversion is more prevalent in societies with free markets (vs. places where you take what’s given and like it), one might say that agents following the irrational strategy reflect an assumption that there must be a better deal somewhere (though there isn’t in this game), and that one should not settle lest “unfair” splits become the norm.

I think the “crazy/insane” point deserves distinction since it hinges on a fundamental economic assumption (rationality), and so much interesting research surrounds how, when, why, and more importantly, to what extent this assumption is not valid in various interactions. (Also, in practice, the most reliable profit maximizer is likely to be a sociopath–not commonly considered “sane.”)