Humans cry as a response to emotions, not just physical pain - and that makes us different from all other animals, as far as scientists can tell. But while we all cry, we cry in different ways. Why do you cry? How often do you cry? And how do you feel after you cry? In the Opinion piece "I Cry, Therefore I Am," the neuropsychiatrist Michael Trimble explains: In 2008, at a zoo in Münster, Germany, a gorilla named Gana gave birth to a male infant, who died after three months. When was the last time your cried? Does where you are and who you are with affect how - or if - you cry? Has growing older changed why or when you cry? How do you feel after you cry? If you don't often cry, how else do you express your emotions?