Study: Dogs May Have Evolved 'Puppy Dog Eyes' To Melt Hearts Of Humans

MIAMI (CBSMiami) -- New research finds 'puppy dog eyes' are an evolutionary trick to manipulate humans.

A study from scientists in the US and the UK says pet pooches have evolved human-like eyebrow muscles, which let them make the sad faces that melt the hearts of their owners.

Any dog owner can confirm our four legged friends are masters of manipulation.

''Most of the time he's looking at me with his big eyes asking for food," says dog owner Irena Smith.

Now scientists say it is more than the prospect of a treat that leads to those puppy-dog-eyes, its evolution.

The research compares the anatomy and behavior of dogs and wolves and suggests dogs facial features have changed over thousands of years to allow them to better communicate with people.

"That sad puppy dog expression must have come into play sometime after the first dogs were domesticated," explains Anne Burrows, the study author and lead anatomist at Duquesne University.

Authors say the inner eyebrow raising movement triggers a nurturing response in humans because it makes the dogs eyes appear larger and more like a baby.

"That eyebrow movement hijacks our emotions, triggers some kind of nurturing or caregiving response like what you see in human parents paying attention to their own infants," says Burrows.

Researchers agree saying it is a dog's face that helps bond them to their owners, even more than a loveable tail wag.

In a prior study, researchers found that puppy dog's eyes are so effective, that dogs with more expressive faces often get adopted faster from shelters.