Study: Scientists find reason for ‘puppy dog eyes’

(CNN) – Every dog owner has been there; brought to your knees by your favorite canine’s “puppy dog” eyes.

Well, a study published Monday says evolution may be behind that famous facial expression.

According to researchers, a specific muscle causes dogs’ inner-eyebrow to raise and that makes their eyes appear bigger and more infant-like.

The scientists believe dogs do it specifically to get a reaction out of humans.

Researchers say canines adapted the expression as they became domesticated over 33,000 years ago.