Scientists have found that just like humans and other primates, dogs get jealous too!
The Austrian team paired up pooches and asked the dogs to hold out a paw on demand from the handlers. One of the dogs was given a treat whenever it cooperated, the other dog went unrewarded. Quite quickly the un-treated dogs detected the inequality and refused to cooperate further. That this was down to jealousy was suggested by the fact that when the dogs were tested on their own - i.e. without a second dog being rewarded alongside them - they continued to cooperate despite the absence of any treat.
"This shows that dogs have the same basic brain programming for inequity that we do," says study author Friedericke Range, "although it is probably better developed in higher animals like primates that also gauge the size rather than just the sheer physical presences of a reward."
The team suggest that the result is an evolutionary mechanism for fostering cooperation between pack and social animals like dogs, wolves and monkeys. "When you see that someone doing the same work as you is getting more reward it makes sense to refuse to cooperate until equality is restored," says Range.