Curious Questions: Why can’t we resist puppy dog eyes?

It's no accident that your heart melts when dogs gaze into your eyes — it's simply a fact of thousands of years of evolution and selection, as Martin Fone explains.

A couple of weeks ago, I took a look at the mystery of when the first dog was domesticated — and by whom.  The answer is at least 14,000, and quite possibly as much as 35,000 years ago. As for who, the question is far harder to pin down — but it seems certain that dogs and humans teamed up long before we moved from hunter-gatherer to agrarian societies.

Its unique position amongst domesticated animals, a largish mammal that is principally a carnivore, suggests that its value came from its ability to assist in hunting other prey and providing protection. Over the millennia breeding, by design or chance, introduced other characteristics, morphing anatomical features, and enhancing behavioural traits which strengthened their value and the bond between dogs and humans.

One of its key attributes is its ability to interpret and follow verbal commands and gestures from their human owners, something our closest relative, the chimpanzee, or their closest living relative, the wolf, cannot do.

And it is all down to the eyes.

Eye contact helps a dog to know when a command is directed at them; conversely, their inability to see a human’s eyes often leads them to ignore an instruction. When unable to solve a problem on their own, they seek eye contact for help and guidance.

From an early age a puppy will seek to establish a strong bond with their owner through prolonged periods of eye contact, something many of us find so hard to resist and which makes us ready to forgive even the most egregious infractions of prescribed behaviour.

What we are experiencing during these bouts of mutual gazing is a rush of the love hormone, oxytocin, which makes us want to nurture and protect, analogous to the feelings that are induced when a parent gazes on their new-born infant. As humans took more overt control in breeding those characteristics which led to the modern domestic dog, preference was given to those that elicited in us a desire to lavish care and affection.

We also have a distinct preference for breeds that exhibit what scientists call paedomorphism, features which even in mature specimens make then look infant-like, such as large foreheads and large eyes.

Paedomorphic facial features are further exaggerated by certain facial movements and here is where the dog has become particularly cute. They have developed a muscle which allows them to raise their inner eyebrow, known as the AU101 movement, making their eyes appear larger, more baby-like and more appealing. We become like putty in their paws when they give us this look as it resembles how we look when we are sad. Breeds that have perfected more exaggerated AU101 movements, research has shown, were more likely to be rescued from a welfare shelter than others, giving them a distinct selection advantage.

What the AU101 movement also does is expose the white parts of the sclera in dogs’ eyes. Unique amongst primates we have a visible white sclera and studies suggest that we significantly prefer animals that have a visibly white sclera to others. All this has led some scientists to conclude that, through the dog’s long relationship with humans, genetic pressure on their facial muscle structure has caused additional muscles to evolve, solely for the purpose of enhancing the bond between them and us.

Unless you have an adamantine heart, it seems you are powerless to resist the poignancy of the stare. It makes you wonder who really wears the trousers in the relationship…