Shayna, a Labrador retriever, makes “that face” that seems to get dogs attention and treats. (AP)

Shayna, a Labrador retriever, makes “that face” that seems to get dogs attention and treats. (AP)

This diagram shows the muscles that make eyes expressive. Dogs have them (left) and wolves don’t (right). (AP)

This diagram shows the muscles that make eyes expressive. Dogs have them (left) and wolves don’t (right). (AP)

This female red wolf can’t make those “sad puppy eyes” like a dog can. (AP)

This female red wolf can’t make those “sad puppy eyes” like a dog can. (AP)

Lexy, a therapy dog in North Carolina, has put “puppy dog eyes” to work. You can’t help wanting to give her a treat and pet her. (AP)

Lexy, a therapy dog in North Carolina, has put “puppy dog eyes” to work. You can’t help wanting to give her a treat and pet her. (AP)

Behind Puppy Dog Eyes

Posted: September 3, 2019

What’s the science behind that irresistibly cute face your dog makes? Researchers have some new ideas.

People have kept dogs for thousands of years. Little by little, dogs have gone from wild to domesticated. Now researchers think people preferred pups that made cute, sad faces. People bred those dogs. As they did, generations of dogs developed the muscle that makes the famous “puppy dog” face. Pooches use the muscle to raise their eyebrows and make the babylike expression. Guess what creature doesn’t have that muscle. The wolf!

“You don't typically see such muscle differences in species that are that closely related,” says Anne Burrows of Duquesne University in Pittsburgh. She is an author of the puppy dog eye study.

Ms. Burrows and her team examined the eye muscles in the bodies of six dogs and two wolves. They found the dogs had a meaty eye muscle to lift their eyebrows and make puppy dog eyes. But in wolves, the same muscle was stringy—or missing!

Dogs differ from wolves in many ways. They have shorter snouts. They come in smaller sizes. And, of course, they have more expressive faces. Unlike wolves, dogs pay close attention to human eye contact. They look at a person’s eyes to find out whether that person is talking to them. If a dog can’t hop a fence or get out a door, it will likely look at a human’s eyes to ask for help.

The scientists also recorded 27 dogs and nine wolves as each stared at a person. Pet pooches often pulled back their eyebrows to make sad expressions. The wolves rarely made these faces. The scientists think the muscles developed in dogs because they gave dogs an advantage when interacting with people. The faces mean: “Feed me! Play with me! Take me outside!”