A new study by researcher Takefumi Kikusui of Azabu University in Japan tells us that dogs’ eyes develop tears when they experience emotions such as reuniting with their owner. As Kikusui himself explains, the study suggests that the eyes of dogs transmit tears when positive emotions meet and the mechanism of this reaction could be explained by oxytocin.
The case of the poodle
The researcher began studying this watery behavior when he saw one of his poodles show a different face when nursing his puppies, specifically the eyes which appeared to contain more tear. The tears did not run down the face like in humans, but the eyes were still filled. This phenomenon made Kikusui realize that it was probably oxytocin that was causing tears to build up in his eyes.
The experience of reuniting with the owners
Oxytocin, sometimes referred to as the “love hormone”, is also released in dogs’ bodies, which can occur during interactions. The researcher therefore decided to carry out an experiment during which several dogs were reunited with their master. To measure the volume of tears in the eyes, the researcher performed a standard test. The results clearly showed that the volume of fluid inside the eyes increased when reuniting with their owner, which was not the case when reuniting with people they did not know.
The role of oxytocin
The role of oxytocin was confirmed by adding this substance directly to the dogs’ eyes: there too, the volume of tears increased significantly. Additionally, through questionnaires posed specifically to dog owners, the researchers found that these same owners showed more positive responses when confronted with the face of a dog with teary eyes. This strongly suggests that tear production in dogs evolved so they could form a stronger bond with humans.