Real reason why dogs do puppy eyes at owners - and it's very, very clever

You can never stay mad at a dog for long - no matter how much mud they've run through the house or how many treats they've secretly scoffed.

It's almost impossible to be angry at such a cute, innocent and adoring face.

New research has proven that it's all down to science - and not just because you're a softie.

For decades, scientists and researchers have been trying to figure out how dogs got that 'puppy eye' expression, and Professor Anne Burrows at Duquesne University in Pittsburgh has cracked it.

The results of her research revealed that it's because of evolution and selective breeding.

Dogs have gained a faster facial muscle over time (Getty Images)

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Puppies now have an additional facial muscle, that they never used to before, which explains their downright adorable look.

And their trait to form human-like facial expressions was achieved through thousands of years of artificial selection.

Professor Burrows explained: "Dogs are unique from other mammals in their reciprocated bond with humans which can be demonstrated through mutual gaze, something we do not observe between humans and other domesticated mammals such as horses or cats.

"Our preliminary findings provide a deeper understanding of the role facial expressions play in dog-human interactions and communication.

"These differences suggest that having faster muscle fibres contributes to a dog’s ability to communicate effectively with people.

They've evolved from their wolf ancestors (Getty Images)

"Throughout the domestication process, humans may have bred dogs selectively based on facial expressions that were similar to their own, and over time dog muscles could have evolved to become ‘faster,’ further benefiting communication between dogs and humans."

In the study, researchers analysed the anatomy of tiny muscles used to form facial expressions, called mimetic muscles.

In humans, these muscles are dominated by 'fast-twitch' myosin fibres that contract quickly but also fatigue quickly, which explains why we can form facial expressions rapidly but not hold them for long.

Compared to their wolf ancestors, dogs have more fast-twitch fibres now, enabling small movements such as raised eyebrows.

So if you've ever wondered why your dog looks peculiarly like a human, or why they can gaze so deeply into your soul - it's because humans and nature made them that way.

Do you have a dog story to tell? Contact nia.dalton@reachplc.com.