In a study conducted at the University of Veterinary Medicine, Vienna, researchers trained dogs to discern between photos of humans making two different facial expressions — one happy and one angry.
The dogs studied 15 pairs of photographs. The dogs were then put through a series of tests in which they were shown images revealing either the upper, lower, or side half of the same faces.
According to a press release, the dogs were able to select the angry or happy face more often than would be expected by random chance in every case. The research not only shows that dogs can distinguish between happy and angry expressions, but they can transfer what they learn to understand new clues.
The study also revealed that dogs were slower to associate an angry face with a reward, suggesting that the canine participants already had prior experience learning to stay away from people when they look angry.
"Our study demonstrates that dogs can distinguish angry and happy expressions in humans, they can tell that these two expressions have different meanings,” said Ludwig Huber, senior author and head of the group at the University of Veterinary Medicine Vienna's Messerli Research Institute , in a statement.
“They can do this not only for people they know well, but even for faces they have never seen before."
Researchers say that these findings mark the first solid evidence that an animal other than humans can discriminate between emotional expressions in another species.
source: Messerli Research Institute