For a long time, even the most sentimental of dog lovers that learned more about the unique bond between canines and humans believed that it was all a quirk of natural selection. The argument goes something like this:
“Of course dogs love being around us, early humans had fire for warmth and could provide shelter, food and safety! Dogs that didn’t follow commands or cuddle up at their masters’ feet were left out in the cold, so it’s all about survival.”
However, recent research is dismantling this theory through surprising discoveries about just how responsive dogs are to changes in our emotions, hormones, and even facial expressions.
By comparing this sensitivity in pets to its absence in pack dogs, researchers are realizing that a lifetime of human socialization is responsible for far more of this bond than millennia of evolutionarily shaped behaviors.
The 2020 study “A shoulder to cry on: Heart rate variability and empathetic behavioral responses to crying and laughing in dogs,” published in the Canadian Journal of Experimental Psychology, tested dogs’ response to either their owner or a stranger crying, laughing, or humming.
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Their results found that “dogs showed more behaviours directed toward the person crying, whether the owner or the stranger, than during baseline or laughing conditions… indicating a possible mechanism for empathy-like behaviours.”
While dogs don’t have a “theory of mind” (that is, they’re not able to “put themselves in our shoes,” as empathy is typically described), their bond with human companions grows over time, showing that it is not just a programmed response.
The 2019 study “Emotional Contagion From Humans to Dogs Is Facilitated by Duration of Ownership,” published in Frontiers in Psychology, found that canines “can understand human gestures and facial expressions and can refer to human information in their decision-making. They have come to live together with humans in a group and share the same environment,” a bond that only grows with time.
While one branch of this research concerns itself with monitoring behavior such as dogs’ responses to crying owners, another branch looks at the chemical processes responsible. Two major hormones that have been widely studied and popularized, cortisol and oxytocin, are released in dogs very similarly to humans. Cortisol, which rises in response to stress, is released when a dog senses that its owner is upset or acting stressed.
Conversely, oxytocin is released during periods of sustained eye contact, or during physical closeness such as cuddling. Oxytocin has been called the “love hormone,” but it’s more complicated than that — it can underlie a variety of behaviors but is considered to demonstrate a bond or connection.
The 2021 study “Life experience rather than domestication accounts for dogs’ increased oxytocin release during social contact with humans” compared differences between pack dogs and wolves when interacting with humans. The team found that, contrary to what earlier theories suggest, there are only “subtle” differences between the two. Only when a dog has become socialized to humans do they begin to release more oxytocin, again showing that the bond between a dog and human is at least partly the result of individual attention and relationships, not simply a shift that occurred when canines branched from wolves evolutionarily.
So, what does all this mean? Well, if you’re a dog lover like me, it’s just more proof that the bond we share with our canine companions is a special one. If you’re also fascinated by the complex question of “nature or nurture” and the way it shapes our discussions of human and animal behavior, these studies shed more light on the complicated way that emotions are displayed, perceived, and shared across species!
At the end of the day, the big takeaway is that when you’re sick and your dog comforts you, it’s because they care about you, and not just where their next meal is coming from. Thanks for confirming that for us, science!
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