Let’s say you’d like to encourage everyone to recycle as diligently as my friend does. Instead of instituting an onerous, possibly unpopular mandate, you could nudge. You could, as officials did in the United Kingdom, put up posters of watching eyes to promote good behavior. Or you could copy the authorities in Copenhagen and paint the sidewalk with footprints leading to trash bins. The problem that emerged with this approach, which is neatly summarized by George Loewenstein and Nick Chater in their new book, It’s on You, is that, in retrospect, a focus on personal responsibility in this situation was “misplaced.” “The prevalence of plastics, and plastic waste, has not been caused by individual careless consumers,” they write. “It has been caused by the relentless growth of the plastics industry.”