Why are we so uncomfortable with the idea of being manipulated when we do it to others all the time? When you smile in a job interview, you’re trying to make the interviewer warm to you. When you go on a date, you think about the location, the ambiance, the food and wine—all in an effort to exert influence. Doctors and shopkeepers alike offer options with the intention of pushing people to make certain choices.

You might refer to these behaviors as “nudges”: subtle modifications in the presentation of a set of options that affect a person’s automatic, rather than rational, cognitive processes. In recent years, even governments have seized on the tactic. In 2010, inspired by Nobel Prize-winning economist Richard Thaler, and the book he co-authored, Nudge: Improving Decisions Ab...