NEW YORK (AP) – Scientists say they’ve figured out why dogs can make those sad puppy dog eyes at you. It turns out, it’s because of us.

Thousands of years of living with people encouraged dogs to develop a muscle that lets them raise their eyebrows so they look more babylike. And people may have unwittingly preferred pups that could make that expression.

Researchers suggested this in a study released Monday by the Proceedings of the National Academy of Sciences.

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They showed that this muscle is virtually absent in wolves, the ancestors of dogs.

The researchers believe dogs used this eye muscle to communicate with humans, possibly goading people to feed or care for them – or at least take them out to play.

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