Researchers scanned dogs’ brains while the pooches looked at images of human facial expressions depicting happiness, sadness, anger and fear. Different facial expressions—particularly happiness—sparked distinct activity in different parts of the brain, suggesting that, at the neurobiological level, dogs can read a range of emotions on our faces. The researchers then showed the dogs strangers’ faces with either a happy or neutral expression and analyzed their brain activity. “For the first time—and this was exciting—we found this distinction in the dog brain between two negative emotions,” Cuaya says. It’s also unclear how much of dogs’ ability to differentiate facial expressions is innate and how much has to do with each dog’s experience and learning over time.