By Mark Zastrow
BU News Service

It’s often said that a dog is a human’s best friend. It’s also said that communication is the key to any relationship. So how do we manage to communicate emotion across species? A new study suggests it might be in our hunter-gatherer genes: we appear to be born with the ability to read dogs’ faces.

The findings, published in September in the online journal PLOS ONE, shed light on the evolutionary dawn of our interspecies friendship by asking: Do dogs’ faces convey actual emotion, or are we just convincing ourselves that we can see feelings in their cute, cuddly faces?

“If I speculated on this with dog owners, they would insist that their dogs smile,” says Annett Schirmer, a psychologist at the National University of Singapore and the study’s lead author. “However, if I talked to colleagues, they would be skeptical and suggest that we likely just anthropomorphize dog expressions.”

While previous studies have tried to distinguish a range of emotions in dogs based on praise, reprimands, and the dreaded sight of nail clippers, Schirmer and her colleagues took a simpler approach, considering only positive and negative feelings. To obtain the equivalent of a smile, they snapped pictures of 24 dogs of various breeds just as their owners gave them a toy or treat; for a sad face, they took pictures again after their owners left the room and the dogs began to show signs of negative feelings like whimpering.

The researchers then asked over 60 people to evaluate the dogs’ facial expressions in two ways. One was simply rating them as a positive or negative. The other was more subtle: the researchers observed how quickly people could identify positive and negative words after seeing the canines’ faces. This exercise attempted to recreate the snap judgments of emotions that we make when looking at human faces. The team found that not only could dog owners identify whether the dog was in a positive or negative emotional state, but so could people who had never interacted with dogs.

Harris Friedman, a psychologist at the University of Florida who coauthored a previous study of how we recognize dogs’ emotions,  was impressed by the experiment’s focus. “It simplified our study, reducing looking at six emotions to two (positive and negative), which I think was a really good way to try to…get a better handle on it.”

But what intrigues him most is what such innate communication says about the roots of our species, tens of thousands of years ago. While still speculative, he agrees that it provides “additional evidence” that dogs may have evolved facial expressions to emote to our nomadic ancestors as they learned to coexist, cooperate, and get ahead.

But both Schirmer and Friedman note that there could be another explanation dating back even further: humans and dogs may simply have inherited the same facial expressions from our common mammalian ancestors.

The answer could be a combination. Schirmer notes that studies have shown that non-domesticated canines make positive facial expressions that humans can recognize, but not sad faces. Perhaps humans and dogs could always read the joy on our faces, but had to coevolve to share sadness.

To settle it, Friedman thinks an improved archeological record of dog domestication will provide clues. He also notes that most people who’ve never played with dogs still have cultural knowledge of them: “People watch TV and are exposed to dogs in a myriad of ways.” A logical next step is to study indigenous cultures with no experience with dogs.