It’s our own darn fault. Humans are the reason why dogs can melt our hearts with their sad puppy eyes. That look, you know the one, where your pooch stares at you, and then you give in to whatever they are begging for—a hug or belly rub. An extra treat, or perhaps, little Suede is begging to lick your spoon with the last bit of fro-yo.
Research published in the journal Proceedings of the National Academy of Sciences (PNAS) revealed that there is a scientific name for that look. It is known as the AU101 movement. Your canine companion and their ancestors have been perfecting this look for thousands of years.
Scientists hypothesize that over time, domesticated dogs developed a muscle to raise the inner eyebrow, which produces the AU101 movement. That same muscle, which is responsible for the internal eyebrow movement, does not exist consistently in the closest living relative of the dog, the gray wolf.
The published study used cadavers of deceased animals, who died naturally. Researchers dissected and analyzed the facial muscles of six domestic dogs and four wild gray wolves. The breed of dogs used was; a mongrel, Labrador retriever, a bloodhound, Siberian husky, Chihuahua, and German shepherd.
The researchers discovered that all six of the dogs examined had a large prominent muscle around the eye called the levator anguli oculi medialis (LAOM). This muscle was absent in the wolves. Anatomically, dogs and wolves are similar except for this eye muscle. 
Eyebrow movement plays a considerable role in human interpersonal communication. Perhaps because this movement makes a dog’s eyes appear larger, showing more of the white of the eye and giving them a childlike appearance. The inference is that dogs with expressive eyebrows evolved because of human’s unconscious preference, the expressive eyebrow made them look more like an infant. Researchers believe that this preference influenced selection during domestication. The “look” stirred a desire in humans to want to look at the dog because it created the illusion of human-like communication.
Scientists have plans to conduct more research on the interaction of humans and a greater variety of dog breeds in the future.
For now, we have a better understanding of how dogs make those adorable sad eyes. Although we don’t know what dogs are communicating when they display the look–in the meantime–Suede can continue to have the last bit of fro-yo on my spoon.
Regular visits to a veterinarian licensed by the Department of Consumer Affairs’ Veterinary Medical Board will help to keep your canine companion happy and healthy. To check their license status visit: search.dca.ca.gov
