18.06.2020: A recently published study by Vetmeduni Vienna shows that dogs dislike inequity regardless of breed. According to the study, dogs bred with a focus on cooperative traits, such as sled dogs, exhibit the same sense of fairness as dogs bred for other characteristics, such as hunting dogs.

Inequity aversion, the resistance to inequitable outcomes, has already been demonstrated in a large number of animal species. One explanatory model for inequity aversion is that it co-evolved with cooperation. Dogs in particular are well suited to examine this assumption intensively. Researchers from the Domestication Lab at the Konrad Lorenz Institute of Ethology and the Messerli Research Institute at Vetmeduni Vienna now analysed, whether more cooperative breeds have a more negative response to inequity than breeds in which cooperation is less pronounced. In order to test this hypothesis scientifically, researchers examined 12 representatives of “cooperative worker” breeds and 12 individuals of “independent worker” breeds. The study provided no support for the co-evolution of inequity aversion and cooperativeness. According to the study, dogs display inequity aversion, and breed or breed characteristics have no significant influence on inequity aversion.

No evidence of link between cooperativeness and inequity aversion

The study found that cooperative worker breeds and independent worker breeds do not differ in the extent to which they are inequity averse, though it did find evidence that the breeds may differ in their willingness to exhibit a desired behaviour for humans. According to Jim McGetrick from the Konrad Lorenz Institute of Ethology, “In our ‘paw task’, individuals of cooperative worker breeds were more willing, than independent worker breeds, to give their paw without a reward. The cooperative worker breeds also tended to be more sociable than the independent worker breeds, spending more time in proximity to their canine partners.”

Paw task: 20 slices of sausage, but not for everyone

In the so-called paw task, two dogs were tested at the same time under three different reward scenarios. In each of the scenarios, both dogs had to alternately give their paw on command.

In the first scenario, both dogs were rewarded with a piece of sausage for giving their paw. The second scenario was an inequitable scenario in which only one dog was rewarded for giving its paw whereas the other dog was not rewarded. In the third scenario, one of the dogs did not receive a reward for giving the paw and the second dog was not present.

This was followed by a food tolerance test. Here the dogs were shown 20 slices of sausage in a bowl and were allowed to feed together until the sausage was eaten while their behaviour was observed. At the end of this test, the third activity was a free interaction session in which the dogs were allowed to approach their human partners to be petted. Here, too, their behaviour was scientifically observed.

Indications of behavioural differences as a result of breeding selection

“Overall, our results do not provide support for the hypothesis that inequity aversion and cooperation co-evolved. However, they illuminate potential differences in selection pressures experienced by cooperative worker and independent worker dog breeds throughout their evolutionary history,” says McGetrick. Against this background, the researchers see exciting possibilities for future studies focused on a better understanding of the differences between individual dog breeds.

The article “No evidence for a relationship between breed cooperativeness and inequity aversion in dogs” by Jim McGetrick, Désirée Brucks, Sarah Marshall-Pescini and Friederike Range was published in Plos One.