Adding to that, and reflecting on my own thought processes related to giving, I think this is a good case illustrating the interactions between levels of causes in human behavior. Proximately, I often go through with a charitable act despite fretting that it will be boring, too much trouble, too costly, or otherwise unpleasant. But upon doing it, or soon afterwards, I feel a sort of euphoria I would associate with the endorphin effect described in the NY Sun article.
I will suppose that the euphoria and the associated brain chemistry register somehow in my mind -- in behaviorist terms, an association is reinforced between the feeling and the act of giving -- and this association comes into play the next time a choice for giving arises. But even if so, the association is barely liminal, and I don't reflect along the lines of 'I'll get a nice endorphin rush if I go through with this.' Rather, I think along the lines of 'good people do things like this, and I want to be a good person despite the short-term fuss I will have to endure' -- and I think the euphoric brain chemistry is a bonus (and should be seen as a second-order cause) that keeps acts of giving on the list of thinkable, possible alternatives. The next time I am faced with a choice to give or not to, I will have inarticulate impulses pushing for it, and these impulses will be rooted in brain chemistry.
I do expect some people will disagree so please leave a comment... Trace