(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.
That’s not the only mannerism dogs have slowly learned to use to melt our hearts.
The study notes that dogs are better than other animals at using communication cues like pointing gestures, gazes, and keeping eye contact.