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Scientists Say ‘Puppy Dog Eyes’ are an Evolutionary Trait to Make Dogs Cuter

A new study suggests domesticated dogs evolved the ability to make themselves look like babies so humans would pay them more attention.

by Gavin Butler
19 June 2019, 3:56am

Image via Flickr user st0l1, CC licence 2.0

Let’s talk about dogs. Why are they so cute? What is it, specifically, about this particular species of animal that humans tend to find so irresistibly charming? Sure they’re loyal, and kind, and sometimes whimper to themselves while having nightmares. They look funny in t-shirts. But what is the actual, scientific basis for our emotional connection to man’s best friend?

Well, a new study published in the Proceedings of the National Academy of Sciences of the United States of America suggests that dogs’ eyes have a lot to do with it—specifically their eyebrows, which allow them to perform complex facial expressions and elicit an emotional response from humans. The study’s authors hypothesise that “domestication transformed the facial muscle anatomy of dogs specifically for facial communication with humans”, and that “dogs’ expressive eyebrows are the result of selection based on humans’ preferences”.

In other words: domestic dogs have evolved the ability to perform facial expressions such as “puppy dog eyes” because it has historically made them more appealing to humans and more likely to be nurtured by them. They have literally evolved to be “cute”.

To examine this phenomenon, researchers cut open a bunch of dog heads and wolf heads and compared the facial muscles in each. What they found was that the domestic dogs all possessed a muscle which allowed them to raise their eyebrows—a muscle that was all but entirely absent in wolves. Behavioural data collected from dogs and wolves further showed that dogs produce a particular kind of eyebrow movement significantly more often and with higher intensity than wolves do—and researchers believe this has a large part to play in how “cute” they are.

The power of this eyebrow-raising muscle is the way in which it "makes the eyes appear bigger, hence more infant-like and potentially more appealing to humans," according to the paper. "This inner brow raise also resembles a facial movement humans produce when they are sad, potentially eliciting a nurturing response from humans."

And so by widening their eyes to make themselves look more like babies and cocking their eyebrows in such a way that makes them look more like sad humans, dogs are able to emotionally blackmail people into giving them more attention—a trait that’s proven extremely advantageous from an evolutionary perspective. As the researchers put it: “dogs hijacked the human caregiving response. The most likely evolutionary scenario is that dogs’ ancestor must have, to some extent, expressed characteristics that elicited a caregiving response from humans. Humans then consciously or unconsciously favoured and therefore selected for those characteristics.”

It’s precisely because we find puppy dog eyes cute—because it reminds us of babies, more or less—that dogs evolved to do puppy eyes in the first place, the study suggests. Dogs have learned that tugging on a human’s heartstrings is the best way to get what they want—and in the 33,000 years since they were first domesticated, they’ve physically evolved to be able to make themselves look sadder, more vulnerable, and more capable of emotional manipulation.

So who’s walking who?

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