This Can Be Harder on Your Pet Than You Realize

dogs read emotional facial expressions

Story at-a-glance -

  • A recent study confirms for dog parents that indeed, your pet is able to read your emotional facial expressions
  • Depending on which facial expressions were displayed, the study dogs responded with increased heart rates or relaxation, and head turns to either the left or right
  • The head turns suggest dogs use different parts of their brains to process human emotions
  • An earlier study concluded dogs can also sniff out human emotions, and adjust their behavior accordingly

By Dr. Karen Shaw Becker

A study recently confirmed yet one more thing those of us with dogs already know — canine companions are able to read human facial expressions. Not only that, but our dogs behave differently when they see certain emotions on our faces.

As part of the domestication process and thousands of years of close contact with humans, dogs have developed certain abilities that allow them to interact and communicate with people. Recent research suggests the canine brain can read emotional cues contained in a person's voice, body odor and posture.1

The facial expression study, published recently in the journal Learning & Behavior,2 involved three researchers in Italy and 26 dogs. The scientists put food down for the dogs and while they were eating, showed them photos of the same two human faces (a man and a woman).

The pictures were deliberately positioned to the sides of the dogs’ line of sight, and showed the humans intensely expressing one of six emotions — anger, fear, happiness, sadness, surprise and disgust. A second face displayed a neutral (non-emotional) expression.

Dogs Take Special Note of Faces Showing Anger, Fear and Happiness

The researchers observed that when the dogs saw facial expressions such as anger, fear and happiness, certain things occurred:

  • Their heart rates accelerated
  • They tended to turn their heads to the left
  • They took longer to begin eating again than when they were shown the neutral face

The scientists concluded the dogs were experiencing more stress while these three particular facial expressions were displayed, and theorized that the happy face caused stress because dogs instinctively view bared teeth as threatening. Interestingly, when the dogs were shown surprised facial expressions they remained relaxed and tended to turn their head to the right. They showed no “side bias” with their heads when shown pictures of sadness, disgust or a neutral expression.

Dogs Use Different Parts of Their Brains to Understand Human Emotions

These study results are further proof of just how closely connected dogs are with people. According to the researchers, the dogs turning their heads either left or right also suggests our four-legged companions use different parts of their brains to process human emotions.

The right side of the brain plays a more important role in regulating the sympathetic outflow to the heart, and is fundamental in controlling the fight-or-flight response necessary for survival. "Clearly arousing, negative emotions seem to be processed by the right hemisphere of a dog's brain, and more positive emotions by the left side," Marcello Siniscalchi of the University of Bari Aldo Moro in Italy told Science Daily.3

Dogs Can Also ‘Smell’ Our Emotions

According to another recent study, dogs can also sense our emotions with their incredibly sensitive noses. And once your canine companion sniffs out your mood, he adjusts his own accordingly. A team of university researchers in Italy and Portugal set out to answer the question, “Do human body odors (chemosignals) produced under emotional conditions of happiness and fear provide information that is detectable by pet dogs (Labrador and Golden retrievers)?”4

For the study, eight human study volunteers watched a 25-minute video designed to provoke emotional states of either fear or happiness. The volunteers’ sweat was collected on pads as they watched the video, and then the samples were pooled to obtain composite “fear sweat” and “happiness sweat” samples. There was also an unscented control sample.

The 40 study dogs were Labs and Goldens fitted with heart rate monitors. Each dog was placed in a small room with his owner and a stranger who had not provided a sweat sample. The two people were seated, reading magazines and not purposely interacting with the dog.

The samples (either fear or happy sweat, or no scent) were diffused into the room from an open vial containing the sweat pads. The dogs were able to sniff the vial itself, but they weren’t able to actually touch the pads.

Behind the scenes, for five-minute periods the researchers evaluated the dogs’ heart rate, body language, movements toward and away from the owner and the stranger, and stress-related behaviors. To goal was to learn whether the dogs would show a consistent set of behaviors in response to the three conditions.

A Whiff of Human Fear Causes Dogs to Feel Fearful

The dogs exposed to the happy sweat sample had fewer and shorter interactions with their owners, and more interactions with the strangers in the room. This suggests the dogs felt relaxed enough to check out strangers, and didn’t need to seek reassurance from their owners.

In contrast, the dogs exposed to the fear sweat sample displayed more frequent and longer-lasting stress-related behaviors, in some cases, for the entire five-minute period. These dogs also sought out their owners rather than the strangers, indicating they were looking for reassurance because they felt stressed.

The dogs exposed to the fear sweat sample also had consistently higher heart rates than the dogs exposed to the happy sweat sample and the control sample.

“While the dogs were clearly responding emotionally to the scent of fear,” writes dog expert Stanley Coren Ph.D., “it seemed as though their response mirrored the emotion that they were detecting in that they were acting in a fearful manner themselves. There was no evidence of aggression toward either the owner, the stranger, or the scent dispensing apparatus.”5

A bigger question for me, as a veterinarian, is how long-term exposure to human stress and emotional imbalances in the home (fear, anger, frustration, etc.) impact our pets’ health without our knowledge.

In the Dog Cancer Series documentary Rodney Habib and I created, almost every researcher we interviewed brought up the role of stress in canine disease, a topic that hasn’t been studied. This Italian study brings up the question of how negative human emotions play into health and disease patterns in pets.

Evaluating the emotional environment of your home is a good idea. I have a hunch future research will validate what we very much suspect is true — that pets in happy homes tend to be healthier and more balanced than pets who live in stressed or sick homes.