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Puppy love: the science behind puppy dog eyes

Puppy dog eyes
(Image credit: Getty Images/K C Alfred)

It's not just puppy dog eyes – there’s a reason why we call dogs a man’s best friend. They’re not only fun and entertaining companions, but they’re loyal and protective and will show you unconditional love. Who else greets you at the door excitedly after a hard day at work? There isn’t anything our dogs wouldn’t do for us and, what’s more, when they look up at us with those “puppy dog eyes” there isn’t anything we wouldn’t do for them. But do they know the power they have over us with their irresistible, innocent looks? How and why do dogs give us those puppy dog eyes and what makes their expressions so hard to resist? We take a look at the science behind those sad eyes and raised eyebrows. 

What are puppy dog eyes?

We’ve all been there. You look over at your pup and they’re gazing up at you with their inner eyebrows raised and their big, childlike eyes wide open. Whether they’ve done something that they’re in trouble for, want a treat after performing a trick or just want to let you know how much they love you, that imploring expression on their face is impossible to resist. It’s the cute factor that melts our hearts and makes us want to take our pooch into our arms for a cuddle. But does your pet know what they are doing when they look at you this way?

How have dogs evolved to communicate with humans?

It turns out that over time dogs have actually developed a muscle in their face, which allows them to create that puppy dog look and win you over. The Levator anguli oculi medialis or LAOM is a muscle which raises the inner eyebrow making your dog’s eyes appear larger and its face younger and more naïve. 

A group of researchers, led by comparative psychologist Dr Juliane Kaminski, at the University of Portsmouth, together with behavioural and anatomical experts in the UK and USA published their findings in 2019 in the Proceedings of the National Academy of Scientists of the United States of America. The study compared the facial muscle structure of six dogs and four wolves. The first gray wolf appeared in Eurasia around one million years ago and dogs evolved from them around 33,000 years ago. According to this research, as dogs have become domesticated, they have also evolved this new facial muscle, which wolves do not appear to share. The only breed that did not have this new muscle was the Siberian Husky, perhaps because this is an ancient breed and still closely related to wolves.

A second study filmed nine wolves and 27 dog breeds to look at their expressions when in the company of humans. It found that dogs were five times more likely to raise their eyebrows and stare intently at humans than wolves. They may still not know why, but researchers believe that puppy dog eyes evolved in dogs to give them an advantage when being selected by a human. It seems like dogs are the only members of the animal kingdom that have evolved this skill, making this one unique weapon for dogs to get what they want from their owners. Whatever the reason, puppy dog eyes are a relatively recent addition to a dog’s armoury and an incredibly effective one!

Puppy dog eyes

(Image credit: Getty Images/Busybee CR)

Why can’t we resist puppy dog eyes?

So we know that dogs have evolved this unique eyebrow lift to better communicate with humans, but why do these puppy dog eyes hold so much power over us? A third study by Kaminski looked at how dogs in shelters behaved in order to get adopted and they definitely moved their eyebrows more when humans were looking at them. The research showed that puppy dog eyes were much more effective than a dog running over to greet a human or wagging its tail. Dogs are very skilled when it comes to eye contact and gestures. This is what makes them easy to train. They learn commands and how to obey and develop strong bonds with their owners with eye contact. But why do we react how we do? 

Firstly, as humans we also rely on our facial expressions and eyebrow movement to communicate. When dogs raise their inner eyebrows, we immediately feel the need to look after them. This could be because this stare increases our levels of oxytocin (the bonding hormone), which gives us a greater connection to our dog. The ‘sad’ look also taps into our empathic side and makes us feel more for our pet. And finally, the wide-eyed expression that puppy dog eyes create mimics the eye shape of babies. So that then brings out our maternal side, which is drawn to that childlike appearance and brings out our nurturing side. We feel a need to care for them when they give us those puppy dog eyes. 

Puppy love

There’s still a lot we don’t know about our dogs and what they’re really thinking. Researchers at Portsmouth University are now planning to study a wider range of dog breeds to understand exactly how puppy dog eyes have evolved and why they’re so irresistible to humans. In the meantime, we’ll just have to keep giving into them! 

Zara Gaspar

Former editor of World of Animals magazine, Zara is a freelance writer with a passion for wildlife. Born in South Africa, she developed a love of animals from an early age. She is currently looking for a bigger house just so she can get a cat and a dog.