HOWDOGS MELT HEARTS
WASHINGTON— Ever wondered how dogs learned to use their “puppy eyes” to bend us to their will?
It turns out our pet pooches have evolved human-like eyebrow muscles, which let them make the sad faces that melt our hearts, according to a new study published on Monday in the Proceedings of the National Academy of Sciences (PNAS).
It involved dissecting the carcasses of domestic dogs and comparing them to those of wild wolves, our best friends’ ancestors, whom they branched off from around 33,000 years ago ( don’t worry, no animals were killed for the research).
A separate part of the study saw scientists videotaping twominute interactions between dogs and a human stranger, then repeating the experiment with wolves, to closely track how much they used a specific muscle around the eye that produced an inner eyebrow raise.
The researchers found two muscles around the eye were routinely present and well formed in the domestic dogs, but not the wolves, and only dogs produced high-intensity eyebrow move
ments as they gazed at the human.
“It makes the eye look larger, which is similar to human infants,” professor Anne Burrows of Duquesne University in Pittsburgh, one of the coauthors, told AFP. “It triggers a nurturing response in people.”
Since the muscles were robust in the dogs but not wolves, “that tells us that that muscle and its function are selected,” she added.
Oxytocin
The current study was led by Juliane Kaminski at the University of Portsmouth and also included researchers from Howard University in Washington and North Carolina State University.
It builds on past work, including a notable 2015 paper by a group of researchers in Japan that demonstrated that gaze exchange between humans and their pet dogs led to a mutual spike in the so-called love hormone oxytocin, similar to an effect seen between human mothers and their babies.
But the latest work could explain how dogs are able to capture our attention in the first place.
The paper also posits two other explanations for what is going on—eyebrow movement may be significant for human-dog bonding “not just because it might elicit a caring response, but also because it might play a role during dog-human communicative interactions.”
Humans tend to pay attention to the upper facial areas of fellow humans during communication, and the dogs could be responding to this dynamic.
A final hypothesis is that exaggerated eyebrow movements expose the white sclera of the dogs’ eyes, which humans also have and find appealing in other animals (other primates have darkened sclera to camouflage their gaze).