Dogs can recognize smiling faces

A new Japanese study has indicated that dogs can recognise smiling faces, which researchers say may have helped them to live with humans.

They can also learn to distinguish a smile, even on the faces of some strangers, said the study. 

The researchers led by Miho Nagasawa of Azabu University trained nine pet dogs using photos of their owners, who were smiling in some of the photos and looking neutral in the others. 

The dogs were trained to touch their nose to photos of their owner's smiling face. Only five of the dogs completed this training. 

These dogs were then shown photo pairs of smiling and blank-expression faces of unfamiliar people as well as of their owners. 

When shown photo pairs of either their owner or a stranger who was the same gender as their owner, the dogs selected the smiling faces more often than would be expected if they were randomly choosing a photo. 

"This study has shown that dogs that live closely with humans are also able to recognise 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," Nagasawa's team concluded in the study. 

The study was published in the July issue of the journal Animal Cognition.