Do dogs know a happy face?

Dogs can tell the difference between happy and angry human facial expressions, a study has revealed.

Researchers from the University of Vienna devised an experiment where 11 dogs were trained to associate either a happy or an angry face with a food reward.

In a subsequent test, the scientists showed the dogs images , either of human faces they had not seen in their training, or of just half a human face.

As lead researcher Prof Ludwig Huber explains here, the dogs' were able to "use their knowledge" of human facial expressions to spot the difference.

Footage courtesy of Clever Dog Lab, Messerli Research Institute