We all knew dogs were smart and have a keen awareness of human emotions. After all, their brains respond to people’s voices the same way we do.

But scientists have debated whether dogs actually recognise emotions in our faces. Now, there’s mounting evidence to support the idea that dogs can, in fact, tell a couple of facial expressions apart.

Here’s Jane J. Lee, reporting for National Geographic:

Biologist Corsin Müller of the University of Veterinary Medicine in Vienna, Austria, and colleagues tested 11 dogs—including Border Collies, a Fox Terrier, a Golden Retriever, a German Shepherd and some mutts—using a touchscreen. The scientists trained the dogs to touch either a happy face or an angry face for a treat.

They presented dogs with either the top half or the bottom half of the faces to ensure the animals weren’t just responding to a smile or the baring of teeth. Emotions show on all parts of a human face, not just the mouth, says Müller, whose study was published February 12 in the journal Current Biology.

After training the dogs, the scientists presented them with parts of unfamiliar faces—the top, the bottom, or the left half (since research shows that dogs typically look at the left side of the face). The dogs trained on happy faces could recognize them in the testing phase, as could the dogs trained on angry faces. However, the dogs trained on angry faces took longer to learn—probably because angry faces have negative connotations.

It’s not too surprising that dogs have this ability. After all, close ties to humans for many centuries have likely led them to evolve these skills; they’ve been bred, too, to read us. Whether or not the same is true for dogs without much human contact is an open question.

If you want to learn more about what animals are thinking, don’t miss NOVA’s upcoming “What Are Animals Saying?” It’s part of our NOVA Wonders series, airing April and May of this year.