We know humans get jealous, but does it extend to our furry friends? A new study is among the first to prove man's best friend wants to be their only friend. Researchers at the University of California San Diego monitored over 30 dogs in their own homes. They had their owners ignore them and actively play with a fake dog. They found the dogs were two times more likely to push or touch the owner when they were playing with the fake dog, an indicator that they were trying to break up the connection the owner had with a potential rival.