Every dog owner knows how hard it can be to say no to "puppy-dog eyes," but a new study shines light on how canine facial expressions evolved and why humans are able to understand them so well.

A new study suggests that coyotes, like the ones seen here, have the same face muscle as dogs that's used to make pleading "puppy eyes." jefferykarafa via iNaturalist under CC BY-NC 4.0 The adorable ...

The muscles that allow for the "puppy-dog eyes" in domestic dogs is undeveloped in wolves, suggesting that the adorable look evolved to captivate humans. (Pictured: The author's dog, Smoky.) Courtesy ...

When a baby smiles at you, it’s almost impossible not to smile back. This spontaneous reaction to a facial expression is part of the back-and-forth that allows us to understand each other’s emotions ...