Also, poorer people are probably more likely to imagine themselves as recipients of charity rather than its providers, in which case the exact same self-interest motivation would move the answers of rich and poor in opposite directions.
I think that depends on your definition of poor, which is sadly left vague in this article. If by poor you mean paupers and the truly destitute that are homeless or avoiding that fate only by government handouts/charity then I suspect you are certainly right.
If by poor you mean what some refer to as the "working poor" or people only slighly above the working poor on the economic ladder, then my admittedly limited and admittedly anecdotal experience would contradict it. They tend to be hard working, generous with what little they have, and would be insulted by most suggestions of charity (though I have known a couple to take loans from friends to be paid back when they were able...) In short, my limited and anecdotal experience tends to support the concept in the article that the lower and working classes tend to be generous and helpful.
