Good boy! Puppy dog eyes evolved just for you

Top dog: “We created this infant-like creature,” says scientist Juliane Kaminski.

Is your dog really your best friend? Or is it just manipulating you? A new study has identified eyebrow-raising muscles that help puppies to produce their most irresistible expressions.

If you are a dog owner, you will already be very familiar with “that look”. Maybe your dog makes it when it is time for a walk. Maybe it wants you to sneak them scraps of your dinner under the table. Maybe it’s had an accident on the carpet, and wants to avoid being told off.

The eyebrows go up. The eyes go wide. And your heart melts.

We call it “puppy dog” eyes, but the expression has a scientific name too: “AU101 (inner eyebrow raise)”.

Scientists now believe that dogs evolved to make their expressions even cuter after humans reacted so positively. When the authors of a new study dissected the faces of dogs (that had died for unrelated reasons), they found two facial muscles that were not present in wolves.

The retractor anguli oculi lateralis muscle (RAOL) and the levator anguli oculi medialis muscle (LAOM) connect the ring around a dog’s eyes to either end of its brows. This is what allows them to raise their eyebrows imploringly at humans.

As the muscles are not found in wolves, the scientists believe that these muscles developed after the species split and dogs evolved to become more domesticated. Early humans were more likely to look after dogs they felt sympathy for — so, dogs got better at evoking that sympathy.

“We prefer dogs with […] infant-like, large eyes,” explained Juliane Kaminski, one of the study’s authors, in The Times.

“We see this movement, this raised eyebrow, and it triggers a nurturing response. We want to take care of this thing.”

In fact, two years ago, the same team of scientists found that dogs making the most puppy eyes in a shelter are adopted sooner. When it comes to finding a new home, “AU101: inner eyebrow raise” is more effective than tail-wagging or bounding over to greet people.

Of course, dogs are also very good at responding to humans. If their owners are trapped and crying, for example, dogs will become upset and try to free them. This is known as the “Lassie hypothesis”.

Man’s best friend?

So, are we just being manipulated by 33,000 years of evolution? For a long time, Western philosophers rejected the idea that animals could have feelings, believing that humans were the only ones with the gift of consciousness. Animals do not think and feel; they react on instinct. If your dog looks sad, it is only because it has learned that this will get you to do what it wants.

But scientists are beginning to question this. A wave of new research suggests that animals are more aware than we first thought. Dogs are a great example. They produce the relaxation hormone oxytocin when being cuddled by their owners, and the stress hormone cortisol if left alone for too long. Their bond with humans is very real.

You Decide

  1. Will this news change how you react to your dog’s cutest faces?
  2. Do animals have feelings?


  1. Write a short story through the eyes of a pet dog. How does it get what it wants? Include sensory language.
  2. Draw a diagram to explain how dogs evolved from wolves over several thousand years. Which features changed during that time?

Some People Say...

“A dog is the only thing on Earth that loves you more than he loves himself.”

Josh Billings, US writer (1818-1885)

What do you think?

Q & A

What do we know?
A new study, published on Monday, looks at the “evolution of facial muscle anatomy in dogs”. Scientists dissected dog heads of a Chihuahua, a Labrador, a Bloodhound, a German Shepherd, a Siberian Husky and a Mongrel. They all had the LAOM muscle; four dissected wolf heads did not have it. The RAOL muscle was less pronounced in wolves than in all of the dogs, except the Siberian Husky (one of the most ancient dog breeds).
What do we not know?
The findings suggest that these facial muscles developed after dogs became domesticated. However, we do not know exactly when, or why, it happened. In this way, evolutionary science is not exact — scientists can suggest that it happened because humans responded better to wide-eyed dogs, but they cannot know for certain.

Word Watch

New study
Published in PNAS, or Proceedings of the National Academy of Sciences, on Monday. You can read the full study in Become an Expert.
Dogs evolved from wolves through a process of artificial selection. In other words, humans bred wolves with certain characteristics that they wanted to keep, such as smaller teeth or a more docile nature. Different breeds of dog were bred for different purposes.
Tame, and able to live alongside humans (as opposed to wild animals).
A reference to a fictional dog called Lassie, that originally appeared in a 1940 novel by Eric Knight. Lassie also had her own TV show, comic books and movies. Stories about Lassie usually involve her saving the day, or being reunited with her owners.
33,000 years
Scientists believe that this is how long ago dogs split from wolves, and started the long process of becoming domesticated.
The state of being aware of your surroundings. It is one of the most mysterious areas of human study, as we do not know where human consciousness comes from, or what we share it with.


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