It’s always the same outward signs, the rapid tail wagging, jumping up and down and irrepressible tongue lashing. Every dog owner regularly experiences this joyful reunion with their pet after a long period of separation.

We must add a more discreet sign to this list of highly demonstrative behaviors. In a study published Monday in the journal Current Biology, researchers showed that dogs also produce tears when they find their owners.

“We had never heard of animals shedding tears in joyful situations, such as reunions with their owners,” said one of the study’s authors, Takefumi Kikusui of Azabu University in Japan, in a statement, citing a likely “world first.”

Several researchers measured the number of tears produced using a widely used test, the Schirmer test (consisting of a strip placed under the eyelid). They used a baseline level from when the dog was in its familiar environment with its owner.

The exact number is not precise, but between five and seven hours of separation, the number of tears increased “significantly” within five minutes of the dog being reunited with its owner.

The number of tears was also higher when the dog was reunited with its owner rather than with another person.

According to scientists, this production of tears is linked to the presence of oxytocin, nicknamed the “love hormone”.

Furthermore, they tried to understand what practical role these outpourings could play. To do this, owners were asked to rank photos of their dogs by how much they made them want to care for them.

Videos, audio, and photos where artificial tears had been administered to the animal were ranked “significantly” higher, according to the study.

“Dogs who exhibit misty eyes during interactions with their owners may lead their owners to care for them more,” Takefumi Kikusui argued.

For human nature, crying infants lead parents to pay more attention to them, the study points out.

Canines, domesticated like no other animal, have developed specific communication skills over time. Eye contact has been shown to play a role in the relationship between a dog and its owner.

Scientists would like to study whether dogs produce tears when they meet other dogs.