Several game-theoretical lab experiments helped establish the belief that economists are more selfish than non-economists. Since differences in behaviour between experiment participants who are students of economics and those who are not may be observed among junior students as well, it is nowadays widely believed that the origin of the greater selfishness is not the training they undergo, but self-selection. In other words, selfish people voluntarily enrol in economics. Yet, I argue that such explanation is unsatisfactory for several reasons. I (...) also suggest alternative explanations for the observed differences, which have been so far unduly disregarded. (shrink)