In the study, the amount of tears in the dogs was measured in different situations with a so-called Schirmer test where a strip is placed under the eyelid.
In the first test, the dogs were allowed to socialize normally with their owners.
On the second occasion, the dogs were reunited with their owners after being separated for about seven hours.
It was then discovered that the dogs' tear production increased "significantly" at the reunion.
The researchers believe that the reaction is caused by the hormone oxytocin, which is secreted during, among other things, breastfeeding and touching.
Oxytocin is also called the "love hormone" because it is considered to strengthen the relationship between individuals.
- It is possible that dogs become teary-eyed so that the owners will be more inclined to take care of them, says Takefumi Kikusui, one of the researchers behind the study, to the AFP news agency.