Knowledge of the model increases the likelihood of the behavior that the model claims to explain. And no one thinks this is a problem for the truth claims of the model (about fundamental human nature)? I had an argument with some fellow students about this in grad school, and they just didn’t get it.

After a cursory read, I don’t see enough evidence in the paper to suggest that advanced training in Economics causes people to behave selfishly. I’m much more inclined to ask the same question you do near the end of this post–What if economics majors and grad students are naturally inclined to be more selfish, and are thus naturally more inclined to study economics? In fact, it seems the authors themselves offer exactly this interpretation in a footnote on page 8. Perhaps the question should be “Does studying economics exacerbate greediness?” (Or “diminish altruism,” alternately–it seems hard to ask an equivalent question without a strong subjective bent.)