Psyblog has a post on psychology of money, a round-up of recent research on money and X, where X = shopping, gambling, sex, happiness, ... Here's the abstract of what this post describes as "saddest study of all" by Kathleen D. Vohs, Nicole L. Mead, Miranda R. Goode:
Money has been said to change people's motivation (mainly for the better) and their behavior toward others (mainly for the worse). The results of nine experiments suggest that money brings about a self-sufficient orientation in which people prefer to be free of dependency and dependents. Reminders of money, relative to nonmoney reminders, led to reduced requests for help and reduced helpfulness toward others. Relative to participants primed with neutral concepts, participants primed with money preferred to play alone, work alone, and put more physical distance between themselves and a new acquaintance. [link; the text and commentary may require subscription]
Thanks to The Situationist for the pointer.