Scientists—and dog lovers—have long known that dogs are remarkably good at interpreting our laughs, frowns, and tears. But the biology behind this ability has remained largely unexplored until now. In a study published in the Cell Press journal iScience on August 7, researchers peered inside the brains of dogs as they viewed images of various human expressions. The brain scans revealed that dogs process smiles in a unique brain region and, for the first time, provided evidence that dogs can distinguish between negative facial expressions, including anger, sadness, and fear.