clipped from: scienceblogs.com   

Be nice to me or I might not talk to you. Or worse, maybe I will talk to you...

ResearchBlogging.orgRecently published research shows that individual humans will be nicer (more altruistic) when there is the possibility that the recipient of an act can respond verbally. The paper, "Anticipated verbal feedback induces altruistic behavior" is published in Evolution and Human Behavior for March.

Apparently, there is a tendency under different conditions to give either nothing or half of the money.
In any event, the key finding here is that under conditions where feedback was going to happen, the "dictator" (divider of the money) more often gave away half of the cash.