‘Puppy dog’ eyes came of dogged evolution
NEW YORK — What’s behind those hard-to-resist puppy dog eyes?
New research suggests that over thousands of years of dog domestication, people preferred pups that could pull off that appealing, sad look. And that encouraged the development of the facial muscle that creates it.
Today, pooches use the muscle to raise their eyebrows and make the babylike expression. That muscle is virtually absent in their ancestors, the wolves.
“You don’t typically see such muscle differences in species that are that closely related,” said Anne Burrows of Duquesne University in Pittsburgh, an author of the study released Monday by the Proceedings of the National Academy of Sciences.
Dogs differ from wolves in many ways, from having shorter snouts, smaller sizes and more expressive faces. And unlike wolves, dogs heavily rely on human eye contact, whether to know when someone’s talking to them or when they can’t solve a problem, like hopping a fence or getting out the door.
Burrows and her colleagues examined the eye muscles in the cadavers of six dogs and two wolves. They found dogs have a meaty eye muscle to lift their eyebrows and make puppy dog eyes. But in wolves, the same muscle was stringy or missing.
The scientists also recorded 27 dogs and nine wolves as each stared at a person. Pet pooches frequently and intensely pulled back their eyebrows to make sad expressions, while the wolves rarely made these faces, and never with great intensity.
The researchers believe dogs, over their relatively short 33,000 years of domestication, used this eye muscle to communicate, possibly goading people to feed or care for them — or at least take them out to play. And people, perhaps unwittingly, obliged.