Marketplace's Kai Ryssdal interviewed IPA Founder and President Dean Karlan on why people give.

Read an excerpt below, or watch and/or read the full interview here.

Ryssdal: So this is, perhaps, the most basic question of all when we're talking about philanthropy and charity, but why? Why do we give?

Karlan: You know, first of all, I have something fairly obvious to say, which is people do give for lots of different reasons. So there's some easy low-hanging fruit that do explain a lot of people's giving, which is to be part of something, to be part of a greater cause. And the striking thing about that and the tension that that creates is the question of whether people are giving simply to be part of a cause or because of what that cause actually accomplishes and how effective it is.