system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the biological advantage of expressing sadness by leaking liquid from the eye sockets (crying) and why do some animals also do that?
gpt
Crying isn't just expressing sadness, although that's definitely part of it. It's a response to stress that releases specific chemicals and actually serves to calm the person/animal down.

Visibly showing sadness or distress can be helpful to social animals though. It lets others know that individual needs help or support in some way. It would really surprise me to hear of any solitary animals that also do it.