Ryan Sager studies compassion:

As economists and social scientists have begun to dig around in recent decades into people’s true motives when they give to charity, what they’ve found hasn’t exactly been in keeping with the flattering way we humans like to see ourselves. While altruism may play its part, there are also many other factors at play when we donate: guilt, the desire to boost our social status, the need to feel good about ourselves, even our sex drives. Any attempt to understand why we give or to get us to give more must deal with this dirty and tangled reality.

(Hat tip: Hit & Run)