Does your dog always get their way with you by wearing those big puppy dog eyes?
You’re not alone because many dog owners can’t resist the charm in their dog’s eyes.
But why do dogs have big eyes in the first place?
Why Do Dogs Have Big Eyes?
Dogs have big eyes because they have a unique muscle known as the Levator Anguli Oculi Medialis (LAOM).
The muscle is located on the upper side of the eye and raises the dog’s inner eyebrows.
As a result, dogs’ eyes appear larger, and their face bears an infant-like appearance.
In this article, you’ll find science-backed facts about the size of dogs’ eyes and what gives them the appealing look humans usually describe as the ‘puppy dog eyes.’
NOTE – You might like to read this post about why dogs grow so fast.
A Special Muscle Is Responsible for Dogs’ Big Eyes
As you probably know, dogs are descendants of the gray wolf (Canis lupus).
So they have behavioral and anatomical similarities with their lupus ancestors.
However, dogs have also since been selectively bred by humans and, as such distinct characteristics from wolves, and their big eyes are one of those differences.
In a UK study, dog experts compared wolf and dog eyes.
They found that dogs, unlike wolves, have an extra muscle on the eye that causes them to produce an exaggerated inner eyebrow movement.
The Levator Anguli Oculi Medialis muscle (LAOM) is responsible for a dog’s ability to lift its inner eyebrows.
This muscle and the resulting eyebrow movement give your furry friend the puppy dog eye effect.
Specifically, the eyebrow movement:
- It makes dogs’ eyes appear larger.
- It gives dogs a child-like look (i.e., they show puppy features even as adults).
- It allows dogs to make facial movements like humans do when they’re sad.
But there’s another eye muscle in dogs (except the Siberian Husky) and wolves that emphasize your dog’s eye size and shape.
The Retractor Anguli Oculi Lateralis muscle (RAOL) pulls the dog’s eyelid lateral corner toward the ear and gives a longer-eye effect.
The RAOL muscle also appears more efficient at pulling the eyes’ lateral corner than your dog’s wolf ancestors.
So, did dogs inherit the ‘big eye’ muscle from their wolf ancestors?
Apparently not! Domestication is actually responsible for your dog’s large eyes.
NOTE – You may enjoy reading this post about why dogs look out the window so much or this one asking do dogs have a favorite color.
Dogs’ Eye Size Evolved With Domestication
The experts in the study mentioned earlier didn’t only discover that the LAOM muscle was responsible for your dog’s big eyes and the movement of their inner eyebrows.
They also found that the muscle was completely absent in wolves.
Where dogs have the LAOM muscle, wolves have a combination of some muscle fibers and plenty of connective tissues.
Sometimes, wolves also have a tendon where the LAOM muscle would sit.
These fibers and tissues, combined with the absence of the LAOM muscle, reduced the wolf’s ability to raise their inner eyebrows.
So, the difference between a dog’s and a wolf’s ability to raise their eyebrows and create a ‘big eye’ effect seems to have developed with domestication.
The theory is that dogs who made the ‘big eye’ effect on humans had a better chance of winning the latter’s hearts in the early years of domestication.
As such, these dogs stood a better chance of being domesticated (and getting free food!) than those who tended to be aggressive or shy towards humans.
A 2013 study appears to support this finding. Apparently, dogs in shelters who wore the puppy look had higher chances of finding a home than those who didn’t.
In other words, when dogs look at humans with “those” eyes, it activates the humans’ nurturing response and desire to adopt them.
All this suggests that the development of the ‘big eye’ feature may have played a significant role in dog domestication in the early years.
Humans selectively bred those dogs that had the puppy dog eyes.
And to increase their chance for domestication, our canine friends played the cunning wolves and learned to use their puppy dog eyes to win human hearts.
Just in case you were wondering, this video shows a perfect example of puppy dog eyes. Click the image to play:
But dog experts haven’t yet agreed on one issue: Do dogs intentionally put on the ‘big eyes’ effect?
Related Post: Why Are Big Dogs So Gentle?
Do Dogs Intentionally Wear the Big ‘Puppy Dog Eyes’?
Scientists have confirmed that the LAOM muscle triggers the movement of the inner eyebrows and the dog’s big eyes.
However, there’s still the question of whether dogs intentionally activate their big eyes to communicate with their human friends.
Dogs do not intentionally wear the big puppy dog eyes — or at least, there is no conclusive evidence that dogs consciously activate the eyebrow movement that makes their eyes look bigger.
The exaggerated eyebrow movement could be part of a dog’s normal eye movement.
According to the UK study that confirmed the presence and function of the LAOM muscle, the dogs’ movement of the eyebrows is directly linked to their advanced social interaction with humans.
In other words, dogs and humans use eye contact as a communication cue.
Furthermore, other studies suggest that dogs produce more facial expressions and movements when humans are attentive to their gaze than when they’re not.
This implies that dogs activate the ‘big eye’ effect to directly communicate with humans when the latter looks at them.
Conversely, they won’t wear puppy dog eyes when humans don’t focus their attention on them.
However, recent findings have questioned the intentional and communicative function of the dog’s inner eyebrow movement and the resulting big eye.
A study found that dogs activated the eyebrow raiser more frequently in non-social contexts (i.e., interacting with non-human apparatuses). However, they did this less when the reward was given by a human facing the dog.
Also, the raised eyebrow was not an isolated eye movement but part of the dog’s regular eye movement.
And so, the question remains: Are dogs’ big eyes a communication cue or part of their regular eye movement?
I suppose we have to wait for more conclusive studies to settle that matter once and for all.
NOTE – You might also enjoy this blog post looking at the question – why are my dog’s pupils big?
Final Notes On Why Dogs Have Big Eyes
Why do dogs have big eyes? Here are the key points you should know:
- Dogs have big eyes because the LAOM muscle above their eye activates eyebrow movements that enlarge their eyes.
- Dogs, but not their wolf ancestors, have the LAOM muscle, which may have evolved due to domestication.
- Dogs activate eye movements when interacting with humans and non-humans.
- It’s unknown if dogs’ big eyes are a communication cue or just part of the dogs’ eye movement.
NOTE – You might also like to read this post asking: do dogs like eye contact with humans?
Tim is a proud, vetted, and experienced dog foster carer for a charity helping dog owners escape domestic abuse.
He has years of experience training and caring for dogs, both his own and other people’s.
He is an expert in canine behavior and is highly skilled in dealing with all dogs but specializes in the difficult ones that other people may struggle with.
When he isn’t fostering dogs, he is making friends with other people’s pups!