PhotoHumans may not be the only ones who consider eyes to be the window to the soul. A new study out of the University of Helsinki found that dogs, just like humans, focus most closely on the eyes when deciphering facial expressions.

The study, published recently in the science journal PLOS ONE, determined that dogs look first to the eyes and examine them much longer than nose or mouth areas. Ultimately, the dogs appeared to base their perception of the facial expression on the face as a whole.

This social gazing pattern mirrors that of humans and is being called the first evidence of emotion-related gaze patterns in non-primates. The study’s findings provide modern day support of Charles Darwin’s 150-year old argument that human and non-human animal emotional expressions share evolutionary roots.

Different reactions to threatening faces

Using eye-gaze tracking, researchers noted that images of certain expressions  the mouths of threatening dogs, for example  piqued their attention more than others. In addition to being more attentive to threatening faces, dogs’ viewing behavior was altered upon seeing them; they looked much longer at the faces of threatening dogs. 

This attentional bias to threatening faces may be based on an evolutionary adaptive mechanism, researchers say. The ability to detect and avoid threats represents a survival advantage.

But it appeared this reaction to threatening faces was species-specific, as dogs had a much different reaction to threatening human faces.

Species-specific reaction

Instead of looking longer at the threatening face the way dogs did with conspecifics, dogs averted their gaze when a threatening human face was before them. Both reactions  longer looking and the avoidance response  are survival mechanisms, researchers say.

“Domestication may have equipped dogs with a sensitivity to detect the threat signals of humans and respond to them with pronounced appeasement signals,” said Sanni Somppi from the University of Helsinki.

The scientific reasoning behind the different reactions, according to researchers, is that threatening signals carrying different biological validity are most likely processed via different neurocognitive pathways.

Dog-friendly methods were used throughout the study. Prior to the experiment, the 31 dogs who participated were clicker-trained to stay still in front of a monitor without being restrained. As a result of the positive training approach used (a treat was given no matter what reaction was exhibited), the dogs were highly motivated to perform the task. 

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