Study Says Dogs Read Human Emotions on Faces

Dogs Have Developed Face Reading Skills to Sense a Person's Mood

Oct 30, 2008

A study published in the U.K.'s New Scientist reveals dogs exhibit "left gaze bias," which suggests dogs can detect human emotions by looking at the face.

Virtually every dog owner can tell at least one story of how his dog sensed his mood or emotions. And finally, experts have found scientific evidence that suggests that dogs have evolved and developed "face reading" skills, which means that dogs will look to the human's face for hints about the person's emotions and mood.

The evidence for the claim that dogs can read a human's emotion by looking at the face was published in the October 2008 edition of the U.K. scientific journal, New Scientist. The study was led by Dr. Kin Guo, of the University of Lincoln in the U.K.

This ground-breaking study into a dog's ability to detect human emotions suggests that dogs look to the face for signs of anger, happiness, or sadness - just like humans do.

How Do We Know if Dogs Can Sense Human Emotions by Looking at the Face?

The University of Lincoln study into a dog's ability to read human emotions by looking for subtle changes in facial expression is based on evidence that was first uncovered when studying a phenomenon called "left gaze bias."

The study revealed that dogs react uniquely when presented with a human face and their method of processing and understanding the human face is very similar to human method. When presented with non-human faces, there was no remarkable reaction; but when presented with human faces, the dogs all consistently exhibited "left gaze bias" - a tendency that's never before been seen in non-humans.

What is Left Gaze Bias and Why is it Significant to a Dog's Ability to Detect Emotion?

According to the findings published in New Scientist, past studies have revealed that human faces are "lopsided" when it comes to displaying emotion due to the differences that exist between the two hemispheres of the brain.

The left side of the brain is more involved with displaying emotion, so the right side of the human face (which is controlled by the left side of the brain) more clearly expresses emotion. The left side of the human face - controlled by the right and less emotional hemisphere of the brain - is more void of emotion.

That said, humans have evolved to focus on the more emotional right side of the face, which appears on the left when one is looking at another person. Humans have evolved to gaze toward the left first when examining another person's face for facial expressions and cues that are suggestive of the person's mood or emotion.

This tendency to first gaze toward the left when looking at another human face is called "left gaze bias."

According to the published study, left gaze bias only occurs in humans when they encounter other human faces; the rule does not apply to objects or animals. Dogs exhibited these very same tendencies.

The Conclusions of This Study on a Dog's Ability to Read Human Emotions

Researchers at the University of Lincoln say that left gaze bias is significant because dogs exhibited this tendency when looking at human faces, and only human faces. This study suggests that dogs are looking toward the left for the same reasons that humans exhibit left gaze bias - to examine the more emotion-rich side of the human face.

Dr. Kun Guo's team of researchers performed their study on 17 dogs, who were presented with images of human faces, dog faces, monkey faces, and photographs of inanimate objects.

Each dog's eye and head movements were videotaped and an analysis of the tapes revealed strong left gaze bias only when the dogs were presented with human faces.

"Dr. Guo suggests that over thousands of generations of association with humans, dogs may have evolved the left gaze bias as a way to gauge our emotions," the New Scientist article concluded.