While the smelling and hearing capabilities of a dog put humans to shame, the spatial resolution of their vision is also around seven times lower than ours. So after the close relationship dogs have forged with humans, do they have the ability to understand aspects of non-verbal communication using facial recognition? A recent study conducted at the University of Veterinary Medicine, Vienna has proven for the first time that dogs can tell if we're happy or angry just by looking at our face.

"It seems that dogs dislike approaching angry faces. It had been unknown that dogs could recognize human emotions in this way," study director Ludwig Huber said in a statement. "To better understand the development of these skills, we want to perform similar tests also with wolves at the Wolf Science Center."

Huber and his colleagues split 20 dogs into two groups: One group was trained to touch an image of a happy woman’s face and the other group was trained to touch an angry woman’s face. Researchers placed images side by side on a touchscreen and cut each image horizontally during the training phase so dogs would see only the eye region or only the mouth region. This was done so dogs would not base their decisions on subtle differences between images, like teeth or frown lines.

The majority of dogs used for the study were able to accurately differentiate between happy and angry faces, even when the image was split in half. Dogs that were trained to touch the happy face did so at a much faster pace compared to dogs that were trained to touch the angry face. When the dogs were presented with new faces they had not seen during the training phase, they were still able distinguish between happy and angry using either the eye region or the mouth region.

"We believe that dogs draw on their memory during this exercise. They recognize a facial expression which they have already stored," said first author Corsin Müller. "We suspect that dogs that have no experience with people would perform worse or could not solve the task at all."

Huber and Müller claim the dogs in this study were able to decipher between happy and angry human faces because of their memories from other human relationships. A similar study published in Animal Cognition refuted the notion that dogs are unable to remember events that have happened in the past. Hungarian researchers asked eight dog owners to train their dogs to perform tasks they performed themselves, such as ringing a bell and walking around a bucket.

Dogs were able to perform the task after spending between 40 seconds and 10 minutes behind a screen that hid the objects used for the demonstration. The research team said their findings show that dogs do, in fact, display signs of episodic memory, memory of a specific event in time; semantic memory, the ability to understand meanings and concepts; and declarative memory, the ability to recall facts and knowledge.

Source: Schmitt K, Barber A, Huber L, Müller C. Dogs Can Discriminate Emotional Expressions of Human Faces. Current Biology. 2015.