Sad eyes can mean a lot of things. Although it's possible that the dog is sad, behaviorists believe dogs developed that puppy dog look to mimic the same feelings we have when we look at human babies.

A previous study by the same researchers hypothesized that "dogs with expressive eyebrows had a selection advantage and that 'puppy dog eyes' are the result of selection based on humans ...

It’s been said that a dog is man’s best friend. Perhaps no other animal is as loyal, and with their goofy smiles and puppy ...

Dogs and humans co-evolved. No other species is so closely adapted to living with us. Dogs even have special facial muscles ...

A previous study by the same researchers hypothesized that "dogs with expressive eyebrows had a selection advantage and that 'puppy dog eyes' are the result of selection based on humans ...