The Evolution of Puppy Dog Eyes

Having a hard time resisting your dog’s puppy dog eyes?  New research comparing the anatomy and behavior of dogs and wolves suggests dogs’ facial anatomy has changed over thousands of years specifically to allow them to better communicate with humans.  Yup, it’s all an evolutionary canine plot to win us over.

In the first detailed analysis comparing the anatomy and behavior of dogs and wolves, researchers found that the facial musculature of both species was similar, except above the eyes. Dogs have a small muscle, which allows them to intensely raise their inner eyebrow, which wolves do not.  The authors suggest that the inner eyebrow raising movement triggers a nurturing response in humans because it makes the dogs’ eyes appear larger, more infant like and also resembles a movement humans produce when they are sad.

The research team, led by comparative psychologist Dr. Juliane Kaminski, at the University of Portsmouth, included a team of behavioral and anatomical experts in the UK and USA. “The evidence is compelling that dogs developed a muscle to raise the inner eyebrow after they were domesticated from wolves. “We also studied dogs’ and wolves’ behavior, and when exposed to a human for two minutes, dogs raised their inner eyebrows more and at higher intensities than wolves,” says Dr. Kaminski.

“The findings suggest that expressive eyebrows in dogs may be a result of humans unconscious preferences that influenced selection during domestication. When dogs make the movement, it seems to elicit a strong desire in humans to look after them. This would give dogs, that move their eyebrows more, a selection advantage over others and reinforce the ‘puppy dog eyes’ trait for future generations.”

Dr. Kaminski’s previous research showed dogs moved their eyebrows significantly more when humans were looking at them compared to when they were not looking at them. “The AU101 movement is significant in the human-dog bond because it might elicit a caring response from humans but also might create the illusion of human-like communication,” she says.

Dr. Kaminski and co-author, evolutionary psychologist Professor Bridget Waller, also at the University of Portsmouth, previously mapped the facial muscular structure of dogs. “This movement makes a dogs’ eyes appear larger, giving them a childlike appearance. It could also mimic the facial movement humans make when they’re sad,” says Professor Waller.  “Our findings show how important faces can be in capturing our attention, and how powerful facial expression can be in social interaction.”  The only dog species in the study that did not have the muscle was the Siberian Husky, which is among more ancient dog breeds.

It is not known why or precisely when humans first brought wolves in from the cold and the evolution from wolf to dog began, but this research helps us understand some of the likely mechanisms underlying dog domestication.

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Photo Credit:  Immagy / Shutterstock.com