A smile can go a long way. It can welcome clients into your clinic, brighten a stranger’s day, and just plain make you feel good. And now a study published in the online issue of the research journal Animal Cognition says that dogs can learn to tell apart smiles from blank expressions in photographs of people. But before you go smiling at every dog you see in your veterinary practice—your cheeks might be numb by the end of the day—researchers are unclear whether dogs actually recognize and respond to smiles in real life.
During the study, researchers put five dogs through a training course designed to teach them to react differently to smiling and unsmiling photos of their owner. The trained dogs, all Labrador retrievers or poodles, were tested and all five were able, significantly more often than expected by chance, to discriminate their owners’ smiling faces from their expressionless faces, researchers say. When they showed dogs photographs of unfamiliar faces, they were also able to significantly more often discriminate smiling faces from blank faces, but only if the pictured people were of the same gender as their owner.
Researchers say the results suggest that dogs can learn to discriminate between smiling and expressionless human faces conditionally. Which facial features and changes dogs use to recognize the smiles is unknown. The study says they might have based their choices on the appearance of teeth.