Moreover, lessons from the laboratory and observation of real-world events also help us appreciate factors that may make it easier, in fact necessary, to intervene on a large scale rather than a small one—factors involving not only economies of scale but also channel factors, the communication of social norms or “default” choices (as in the “opt-in” vs. “opt-out” studies), and the effects of mass media role-models, which we have been investigating for many decades