Navajo Celebrate An Infant's First Anger

It was interesting to read that the Navajo celebrate an infant's first smile because they view it as the baby becoming a person. This is very telling about the value that Navajo put on happiness, you become human when you are able to laugh. It was also interesting to read that anger is a healthy emotion for an infant, whereas sadness has adverse impacts. I would think that both anger and sadness would cause