By now you have likely heard of a trending question in social media: women and girls are encouraged to ask the men in their lives how often they think of ancient Rome, with the expectation that they will be surprised to find that the answer is “frequently” or even “daily.” Speaking for myself, I have never kept tabs on how often I think of particular subjects, or of exactly which subjects I think of during a given day. I doubt if many people do. Certainly daily, or at least, almost daily, we all think of our work, our friends, our...