Dogs can experience “Tears of Joy” emotions just like us

Dogs’ eyes can get watery just like humans, but prior to a recent study, there was no evidence that their tears were linked to emotions. Dogs don’t seem to cry when they’re sad, but Professor Takefumi Kikusui began to wonder if dogs experience “tears of joy” after seeing his Standard Poodles’ eyes during emotional moments.

So Kikusui conducted a study to discover if there was a correlation between dog tears and happy moments. His research shows that dogs can shed tears when they see their loved ones after a period of separation. Maybe dog and human emotions are more similar than we thought!

Studying dog tears

Kikusui, a professor at the Human-Animal Interaction Laboratory at Azabu University, Japan, worked with a team of fellow scientists on this study. He became curious about dog tears after he noticed that his dogs would shed tears every time they saw him after a long time apart. One of his Poodles also had a tear in his eye after feeding her newborn puppies for the first time.

Scientists used the Schirmer Tear test (STT) on 18 dogs to monitor their tear production. For the test, a strip of paper needs to be placed under the subject’s lower eyelid to catch tears. Strips of paper were placed under the dogs’ eyes for one minute before and after the dogs reunited with their humans five to seven hours apart. The researchers compared the results of the dogs reunited with those they knew well with their owners.

They also tested STT on 22 dogs after instilling oxytocin in their eyes. Oxytocin is a “love hormone” that helps us feel connected to others. Scientists suspect that’s what causes tears of joy in humans and possibly dogs.

What did they discover?

According to Kikusui, the amount of tears in dogs increases when they are reunited with humans, but not when they meet another person in life. These results suggest that dogs have a special bond with their owners that causes them to shed happy tears.

“Tear volume was assessed by the length of the wet part on the STT. The baseline is about 22 mm, and the reunification with the owner has increased by 10%,” said Kikusui.

When oxytocin solution was instilled into the dog’s eyes, their tear volume increased significantly compared to dogs receiving the control solution. So love may be part of the reason a dog’s eyes light up.

However, the study did not examine other emotions. It’s unclear if dogs shed tears when they’re sad, so there’s a lot to consider. This study is the first evidence that dog tears can be linked to emotions.

Some scientists are skeptical

This is a touching finding for dog lovers, but not all scientists are convinced. Clive Wynne, a dog behavior expert at Arizona State University, said he’ll need more evidence before he’s convinced.

Wynne says there are other possible explanations for the increased tear production. When dogs are excited, they move around more, which can cause more paper to rub against their eyes to produce more tears. Solutions with oxytocin can slightly irritate the eyes, also causing more tears to be produced. However, it seems likely that all dog eyes in the study would respond equally to those potential irritations.

RELATED: Staring a Dog in the Eye Releases Your Love Hormones

So are dog tears associated with positive emotions? They can be! But either way, humans seem to have a stronger emotional connection with dogs that tear up. 74 people rated a series of dog photos based on how much they wanted to care for them. The majority feel most obligated to take care of those with tears.

Next time your dog has tears in her eyes, ask yourself what the context might be. It could be their way of showing that they are excited to see you!