When dog owners return home, their pets usually greet them with wagging tails and slobbery kisses. It turns out these happy reunions may also cause dogs to cry. That’s according to Takefumi Kikusui, an animal behavior scientist at Azabu University in Japan. He measured the volume of tears produced by a group of dogs before and after they were reunited with their beloved owners—and found a significant increase in the animals’ tears following the reunion. But when he tested another group of dogs before and after reuniting with familiar people who weren’t their owners, he found little change. This suggests that dogs’ tears may be tied to their emotions, says Kikusui.