There is a mixture of fact and conjecture here.
Fact – humans have three chemically distinct tears – irritation tears (like when sand gets in your eyes), lubricating tears (normal 24/7 stuff), and emotional tears (when you cry). So if you took someone’s tear and tested it, you could absolutely know if it was someone was sad and crying vs. had a cold.
Conjecture – *why* do we cry when we’re emotional? The leading theories are that A. it serves as a tool to release the chemicals that are trigger our emotions. So we’re literally “crying out” our sadness. and/or B. they serve as a visible sign to others that we emotionally compromised and that, as a social species, there is a benefit to us in knowing the emotional state of other people around us.
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