Batson observed that increased empathy correlates with increased helping behaviour, SEP then describes as follows:
He found that the altruistic hypothesis always made superior predictions. Against the unpleasant experience hypothesis, Batson found that giving high-empathy subjects easy ways of stopping the experience other than by helping did not reduce helping. Against the punishment by others hypothesis, Batson found that letting high-empathy subjects believe that their behaviour would be secret did not reduce helping. Against the self-administered reward hypothesis, Batson found that the mood of high-empathy subjects depended on whether they believed that help was needed, whether or not they could do the helping, rather than on whether they helped (and so could self-reward). Against the self-administered punishment hypothesis, Batson found that making high-empathy subjects believe they would feel less guilt from not helping (by letting them believe that few others had volunteered to help) did not reduce helping.
SEP concludes that this is very bad news for Psychological Egoism - and I think a large part of me is inclined to agree - though I certainly have niggles with the experiment, it does seem like strong evidence in favour of altruism.
My question is this - how have Batson's experiments been received by philosophers in general, and how effective a refutation do they consider it to be?
Any other arguments for/against Psychological Egoism and any interesting extra reading you know of relating to the subject (of Batson's experiments or of psychological egoism) would be most welcome within this context as well.