From Jeffry J. Smith:

Re: Studies may have overestimated our generosity (June 17, 2013): I was very disappointed in the methodology of the Dictator game. By making the recipients anonymous and unknown, the motivation of the giver is completely discarded. I wouldn’t have given in either version of the game, the original or the Las Vegas version. The reason? How would I know the gift would be well used? To me that is the salient feature of giving--how well will the recipient use the gift given. This is why I give to charities where I know the percentage of my donation that goes to the cause. For example, Gospel for Asia, one of my favorite charities, ensures that 100% of my gifts go for the purpose I wish, whether children’s education or water wells in villages with no hygenic water supply.

Given that the motivation of the giver is ignored NOTHING can be concluded from these psychological studies. It is far better to do a demographic analysis of giving and see who gives what to which charity. Then interview a random sample of the significant demographic segments and find out their motivations in giving.