I think we all have empathy. We may not have enough courage to display it.
—Maya Angelou

When my daughter was two-and-a-half, I took her to her first movie. She was princess-obsessed at the time and I had bought tickets to The Little Mermaid. I knew this was ambitious—toddlers are not known for their capacity to sit still for 90 minutes. I had anticipated a short period of awe, quickly superseded by an ants-in-the-pants restlessness. What I had not expected was to hear her wailing by the end of the first song. But a few minutes after Ariel began lamenting her life beneath the sea, my daughter was crying in sympathy for the would-be princess’s plight. That such a young child could feel empathy under these conditions was a revelation. It made me wonder about the physiology of empathy. At what age does empathy develop? What parts of the brain are responsible for it? Why are some people more empathetic than others?