A study points out that dogs can learn to recognize smiles of their owner and may even be able to make out the smiles of strangers.
This ability to discern facial expressions and smiles may have helped dogs coexist with humans, researchers said.
Nine pet dogs were trained with photos of their owners. The dogs were trained to put their nose on the photo of their owner's smiling face.
Later, the dogs were shown photos of unfamiliar people, some having a smiling expression and some others with a blank look. Simultaneously, they were shown photos of their owners.
When the dogs were shown photo pairs of an owner and a stranger of the same gender, they seemed to choose photos with a smiling face.
"This study has shown that dogs that live closely with humans are also able to recognize positive facial expressions, indicating that these dogs have acquired the social skills helpful to survive. The ability to learn to discriminate human facial expressions must have helped dogs to adapt to human society," researchers said.