system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When animals appear to be smiling, are they really doing so out of joy or is it just a human misinterpretation?
gpt
Animal body language and signals are very different from ours.  Apes for example, can be taught to smile as we do, but in the wild, displaying your teeth is a threat or sign of aggression.  Their "happy" smile is an open mouth with no teeth showing.