Scientists in Austria say they have found a basic form of jealousy in dogs.
The Vienna-based researchers showed that dogs will stop doing a simple task when not rewarded if another dog, which continues to be rewarded, is present.
Writing in the journal PNAS, the scientists say this shows a sensitivity in dogs that was only previously found in primates.
The researchers now plan to extend their experiments to look at co-operative behaviour in wolves.
The experiment consisted of taking pairs of dogs and getting them to present a paw for a reward. On giving this "handshake" the dogs received a piece of food.
One of the dogs was then asked to shake hands, but received no food. The other dog continued to get the food when it was asked to perform the task.
