system
Given the following post, respond as if you're commenting on Reddit:
human
eli5: Why do laughter and sobbing with grief appear to be so physically similar, even though they're caused by such different emotions?
gpt
Laughter is originally a reaction to an incoming threat which turned out to be harmless or fake. Crying (sobbing) is for the real threats. Imagine a parent making some sort of angry face at a toddler - if they keep it angry/scary, the toddler would start crying in fear, but if they only keep it for a second and then smile, showing that it was a joke, the toddler would laugh.