What (if anything) morally separates environmental from neurochemical behavioral interventions?

Drawing from the literatures on the ethics of nudging and moral bioenhancement, I elaborate several pairs of cases in which one intervention is classified as an environmental behavioral intervention (EBI) and the other as a neurochemical behavioral intervention (NBI) in order to morally compare them. The intuition held by most is that NBIs are by far the more morally troubling kind of influence. However, if this intuition cannot be vindicated, we should at least entertain the Similarity Thesis, according to which EBIs and NBIs share relevant moral features to the extent that moral conclusions about one are implied about the other in the described pairs of cases. I test this thesis by putting forward a number of possible moral grounds for setting EBIs and NBIs apart, including three of the most promising ones – physical invasiveness, disclosure and avoidance, and inevitability. I conclude that although these promising grounds might not bear the full burden of vindicating the intuition against Similarity by themselves, clustering them together can establish discernible moral separation.