I cannot know how much my child’s being a girl shaped the optician’s thoughts about her emotional state. But I know from my research on the gendering of emotions that people start expecting women and girls to show nurturing and positive expressions early. A different group of researchers analyzed more than 16,000 yearbook photographs of students from kindergarten to college, as well as school faculty and staff. The children showed no significant difference in smiling until age eight or nine, but then the gap started to widen, with girls smiling much more than boys. The difference between girls and boys peaked by the time the students were 14 years old, with girls smiling more frequently and more broadly than boys, and this contrast remained consistent over adulthood.