[chii]

> if I'm happy with the transaction today why should I be less happy tomorrow based on someone else's transaction?

jealousy. Even animal studies have shown that monkeys who sees another monkey receive more reward for the same "work" gets angry (i recall it was some experiment where one monkey got "paid" in grapes, while another was paid in something else less desirable - i forgot what - and initially both were happy, as they did not see each other's payment, but once the monkey saw the grape reward, they refused their reward and got angry).

[strken]

This is a useful strategy. If the other monkey is getting paid in grapes and you're getting feed pellets, why shouldn't you make a play for an equally good reward?

Obviously there are cases where you'll never get the grapes, but that's why we have executive function.