Takefumi Kikusui noticed that when his poodle nursed her pups, her face looked cuter than ever. Later he realised that her eyes looked teary and he wondered if these two facts are related. Being a researcher, he decided to test whether dogs produce more tears in emotional situations and if so, how humans react to that. But instead in the context of nursing, he decided to study dogs that interact with their owners.
Do dogs cry from joy?
The answer is: yes. Or more specifically, they tear up when reunited with their owners after a few-hour separation.
Like us, dogs continuously produce tears to keep their eyes moist. Researchers measured the tear volume of dogs in their normal home environment with their owners present and just after the owner came back home after a 5–7-hour absence. The tear volume clearly increased after the reunion.
But only their owner elicited such a strong reaction. When dogs were left with other dogs for a few hours at a familiar day care centre, they “cried” only when their owner came back, but not if a familiar staff member entered the room.
Additionally, the researchers showed that a drop of oxytocin in dogs’ eyes increased tear production. Oxytocin is a hormone important for social bonding and reuniting with their owners normally causes its level in dogs to rise. Therefore, oxytocin is likely to be one of the causes of dogs tearing up when they are reunited with someone they have a strong bond with.
Do we care when dogs cry?
The answer is: yes. Or more specifically, people more often say that they want to care for dogs with teary eyes.
People were asked to rate photos of dogs’ faces. Some photos were of dogs with normal eyes, while in others, their eyes were teared up (a saline solution was applied to the eyes before taking the photo). People could score dogs on a 5-point scale from negative emotions (frightens me) to positive (want to pet and care for). Teary-eyed dogs scored higher.
Tears are an important signal in human communication of emotional states at all ages and crying children tend to receive care from adults. Therefore, tear production may be one of the tools (in addition to eye contact and raising their inner eyebrows) in dogs’ arsenal to bond with humans and elicit care.
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Image by Helena Sushitskaya from Pixabay.com
Very informative and incredibly fascinating. Anyone who knows and loves dogs should not be surprised by these findings. While the physical manifestation of emotion can be empirically evaluated and even quantified, the impetus and essence of a dog’s love remains, for me, ineffable and immeasurable. Wonderful article!
Thank you! And you are right, we can measure many things, but the essence of our relationship with dogs (or other animals) is immeasurable.