November 13, 2017

Do Dogs Communicate More Than We Think?

Dogs don’t just use their facial expressions to display emotion. They also use them to communicate, a recent study suggests.
By JoAnna Pendergrass, DVM
Results of a recent Nature Scientific Reports study suggest that domestic dogs’ facial expressions are more than just automatic and reflexive displays of emotion; these expressions are also communicative and can be tailored according to human attentional states. Such results, the study’s researchers wrote, “point to a more flexible system combining both emotional and potentially cognitive processes” in dogs.

Many mammals produce facial expressions, the facial architecture of which has been highly conserved across species. Historically, animal facial expressions were thought to be only involuntary and inflexible reflections of an animal’s emotional state. Studies in nonhuman primates have demonstrated an “audience” effect on animal facial expressions, but such empirical evidence has not been reported in other species.

Dogs are especially sensitive to human attentional states. Such sensitivity, honed over nearly 30,000 years of domestication with humans, makes dogs an ideal model to analyze the audience effect on animal facial expression.

In the current study, the researchers used human attentional states and a nonsocial yet highly arousing stimulus (food) to determine whether attention influences dog facial expressions.

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Testing Environment
Twenty-four pet dogs of various breeds and ages were tested. During the video-recorded testing sessions, dogs were tied to a lead and situated about 3 feet from the human experimenter. The experimenter, who did not interact with or make eye contact with the dog, performed 1 of 4 attentional states:
  • Attentive Food – Facing dog, palms displaying food
  • Attentive No Food – Facing dog, palms displaying no food
  • Not Attentive Food – Back turned toward dog, palms displaying food
  • Not Attentive No Food – Back turned toward dog, palms displaying no food

Each dog underwent 2 testing sessions per attentional state.

The researchers coded facial movements using the DogFACS (Facial Action Coding System), which uses underlying facial muscle movements to classify dog facial expressions. They also coded other behaviors, including tail wagging and vocalizing.

Observations
Facial Expressions
The frequency of all coded facial expressions increased with human attention, indicating an audience effect on dog facial expressions.

The “inner brow raiser” facial expression, which resembles facial displays of human sadness, was strongly affected by human attention and has important significance, the researchers noted. This facial expression not only makes a dog’s eyes appear bigger and more infantlike, but also elicits human empathy. According to a previous study, shelter dogs that raise their inner eyebrows when interacting with humans increase their chances of being rehomed. Therefore, dogs can benefit from raising their inner eyebrows in response to human attention.

The “tongue show” facial expression, which can indicate a dog’s general attentiveness, was also heavily influenced by human attention in this study. Displays of food did not affect facial expressions.

Other Behaviors
Human attention increased the dogs’ vocalizations and tail wagging but had no effect on other analyzed behaviors (lying down, sitting, standing, moving).

Bringing It Together
This study, the researchers concluded, “[provides] evidence that dogs are sensitive to the human’s attentional state when producing facial expressions.” Such findings, they believe, suggest that dog facial expressions are communicative, rather than only involuntary facial movements that convey emotion.

 
Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.

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