The people who ask ‘are you mad at me?’ weren’t anxious children. They were children who learned to read a room before they learned to read a book.

In 2003, a researcher named Seth Pollak ran an experiment that changed how psychologists think about childhood environments. He showed children a series of faces morphing between emotions — happy to sad, angry to fearful — and measured how quickly they could identify when one emotion tipped into another. Children who had grown up in homes with physical abuse detected anger faster than any other group. Their brains had tuned themselves to a specific frequency. They were, in the most literal sense...