Researchers have observed that many dogs shed tears when they experience happy moments, notably in the presence of their owners. A recent study published in Current Biology explored this phenomenon and found a link to oxytocin, the hormone often associated with bonding and affection.
The investigation, led by Takefumi Kilkusi at Azabu University in Japan, began by examining the behavior of a poodle nursing a litter. When the animal met the researchers, tears formed in its eyes, though they did not stream down the face as human tears do. The team noted that tear production increased in response to positive interactions, suggesting a potential emotional cue rather than a purely reflexive reaction.
According to the researchers, tears appeared to accompany moments of closeness and trust, aligning with what is commonly described as the motherhood or love hormone. Both dogs and their human companions are known to release oxytocin during social interactions, prompting the team to test whether meeting an owner could trigger tear production in a dog.
To test this, a standardized procedure measured tear volume in dogs before and after reuniting with their owners, comparing those effects to encounters with unfamiliar people. The results showed a noticeable increase in tear volume after owner reunions, while meetings with strangers did not produce the same effect.
Further experiments involved introducing oxytocin to the dogs’ eyes, which caused tear volumes to rise. This supported the idea that oxytocin release plays a role in tear production during moments of human–dog connection, particularly during familiar, emotionally charged reunions.
stronger connections
In a separate part of the study, volunteers were asked to rate photographs of dogs with and without artificial tears. The ratings indicated that people responded more positively to dogs that appeared teary-eyed, suggesting that tears can influence human perception and bonding.
Overall, the findings imply that a dog’s tear production may contribute to stronger bonds between humans and their canine companions. The researchers noted that humans and dogs have a long history of close companionship, and tears could be one more cue that deepens this connection.
The researchers also speculated that dogs might exhibit tearful responses in situations that humans interpret as happy, and they noted the need for further work to determine whether dogs shed tears in response to negative emotions or in interactions with other dogs or breeders. Future studies may also examine whether tear production functions as a social signal within the canine world and how it influences group dynamics among dogs and their human partners.