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According to the study, this “smile” involves a wide open mouth—a gesture believed to have evolved from biting behavior. During play, however, it seems to convey a lack of aggression and ...

Dolphins made a smile-like expression 89% of the time when their faces were in front of their playmate. When seeing this open ...

However, in over a third of cases (33.16%), these dolphin smiles triggered a similar open mouth response from the receiver. In the other 66.84% of cases, the receiver did not smile back and the ...