Moral relativism at its best: your behavior is heavily influenced on how you feel in a particular moment, as revealed by
this paper published in the Journal of Economic Behaviour. The abstract says that those in a bad mood tend to reciprocate (you are good to me, I'll be too, you are bad, I fight back) while those in a good mood tend to be generous (happy, happy, joy, joy, I'll kiss and hug you no matter what).
The paper is also available from
one of the author's home page, and has been commented by
Xenophon, another blog, too.
