Even small children have a sense of fairness and justice: they protest when sweets are not distributed right away, and even prevent others from stealing something from someone, as experimentation shows. Three-year-olds also recognize whether or not a playmate deliberately pushes for a common task. Researchers therefore suspect that sensitivity to equal treatment and fairness was already strong among our ancestors: because they lived together in groups and their survival depended on cooperation, this sense of justice developed. But what about other animals? At our closest relatives, the chimpanzees and bonobos, the sense of fairness seems less clear: in dispersal experiments, these great apes were more concerned about maximizing their own profits, whether or not the food was equitably distributed. In dogs, however, there was initial evidence that they have an aversion to unequal treatment. However, whether this behavior has rubbed off on them by domestication and the long common history with humans or not, remained unclear.
Strike in unfair distribution
That is why Jennifer Essler and her colleagues from the University of Veterinary Medicine, Vienna, once again tested the sense of justice of dogs and wolves in reward experiments. For each two dogs or wolves were placed in adjacent enclosure. They then learned to press a lever on command with the paw to retrieve a food reward. However, there was a catch: in some rounds, only the partner of the leech-kicking animal received a reward, while the active animal went empty-handed. In other rounds, both got a reward, but the preferred treat went to de partner. "The ability to detect this unequal treatment became apparent when the wolves or dogs refused to continue, " explains Essler.
And indeed: both dogs and wolves went on strike when they went empty-handed several times while their passive partner got a reward. They then refused further participation in the trial. The animals behaved similarly if they were disadvantaged in the quality of the reward and received only the inferior food as a reward, their partner but the coveted treat: even then they did not join after a short time. "This reaction confirms even more clearly that it really understands wolves and dogs when treated unequally, " says Essler. The wolves even reacted a lot more sensitively than the dogs - although both were kept and grew up under the same conditions. That this refusal was actually due to the perceived discrimination against the conspecific and not just to the missed or inadequate reward occupied individual tests: If the wolves and dogs completed this experiment without animal partner, they continued, even if in some rounds their reward was missing. "The refusal is triggered accordingly, because the other has received something, but they have not themselves, " explains co-author Friederike Range.
Deep-seated sense of fairness
According to the scientists, these experiments prove that wolves and dogs have a sense of fairness - and that the dogs did not first learn this behavior through close contact with humans. Instead, even the common ancestors of today's dogs and wolves must have possessed a rudimentary sense of justice. The close coexistence in the pack probably plays a role in this: Similar to the groups of our ancestors, the success of the pack depended on the cooperation of the members - and this promotes fair behavior and also a sense of unequal treatment. An indication of this was the extent of the refusal reaction in the wolves: "In the high-ranking animals, the unequal treatment triggered frustration, because they are not used to this situation, not at all or only of poorer quality, " explains Range. "The order in her pack is thus directly related to her response to unequal treatment." Display
However, domestication has left its mark on the dogs - also in terms of their sensitivity to unequal treatment: wolves who were treated unfairly, then kept more distance to the people. The dogs are not. "Even if these four-legged friends do not live directly with humans, they are more accessible to us. Here domestication seems to influence the behavior of the dogs, "says Range. "The close contact with humans as pets could reduce their behavior in such situations rather than trigger it."
- Jennifer Essler (Veterinary University Vienna) et al., Current Biology, doi: 10.1016 / j.cub.2017.05.061