Naturalistic accounts of ethics usually involve the prisoners dilemma in some way. People are motivated to be nice to people because they'll be nice back. This invites the response that this isn't morality at all since it's still selfish. Truly moral behavior involves being prepared to sacrifice your interests.
This is fair enough, but I think it's interesting how this mixes with other moral intuitions.
Say Jack gives Freddie a birthday present because he thinks it's the right thing to do. He takes care to get something his friend likes and goes through all the motions to do it in the right spirit, but just hates doing it. Hated the expense and effort and doesn't take pleasure in Freddie's happiness. Jill also gets a present but loves thinking of what gift to buy and loves seeing Freddie's happy reaction to the present.
My experience suggests we think of Jill as a better person, not just a more pleasant one.
If I'm right, then out of two people behaving identically, we think of the person who's actions are more closely aligned with their self interest as better, which i think is odd.