The debate continues: Do animals have a sense of justice? | Sciences

Hunting begins. Red monkeys are the monkeys that move agilely among the treetops, which are more than 40 meters high. The only way to catch them is through strategy, coordination and cooperation. Three traits are found in chimpanzees in the Tai National Park in Ivory Coast. Everyone knows they have a job. Some chase the monkeys to lead them to where the other comrades responsible for the ambush are waiting for them.

It is the individual chimpanzees that end up catching the colobus, but it was a team effort and distribution of pieces of meat based on what each participant in the hunt contributed. Even the most dominant male receives less meat than a young male if he takes a more active role. This is fair. Is not the sense of justice limited to humans?

Justice exists in all societies. A four-year-old in any culture protests against the unequal distribution of resources. The universality of fairness in humans and the rapidity of its emergence in evolution indicate that it is an evolutionary adaptation. Rather than being just a cultural heritage, it has deeper roots in our biology. What context led us to develop it? The most plausible explanation is that we have become a very cooperative species, and in order to maintain such a community it may be important that the benefits be fairly distributed.

Humans We are not the only animals that depend on cooperation To survive: wolves need to hunt in packs; The ants share the work between digging tunnels, searching for food, and caring for the queen; The meerkats take turns watching to warn the group of predators. Therefore, it is not unreasonable to suggest that we can also share a sense of justice with other animals. Indeed, philosophy takes centuries address this issue. Aristotle believed that without language this quality could not occur and, therefore, only humans possessed it.

Twenty years ago, this philosophical debate catapulted into empirical research. In 2003, it was one The most famous studios about animal behavior have been published to date, specifically addressing the sense of justice in monkeys. It showed one of its authors, Frans de Waal Experience In a TED talk he had a huge impact. The audience bursts out laughing at how easy it is to identify with the subject of study.

Two capuchins are in an adjacent cage, so they can see each other. In front of the cages there is a person with two bowls, one containing cucumbers and the other containing grapes, which are the favorite fruit of these monkeys. Capuchins were trained to perform a task which consisted of picking up a stone from the cage and handing it to a human. In exchange, they are given a food item from one of the dishes.

The first Capuchin correctly delivers the stone, is given a piece of cucumber, and eats it. Then, his partner acts, but receives a grape for doing the same job. When the turn returns to the first and he receives another piece of cucumber, instead of eating it, he throws it furiously at the human, clearly showing his dissatisfaction with the distribution of food. This behavior was interpreted as evidence that the monkeys were reacting aversively to inequality.

Since then, a field of research has opened up that has sought to replicate and extend the experiment to other species. Several studies indicating this have begun to be published micethe crowsAnd cockatoosAnd dog And other primates They are also sensitive to injustice and thus possess the central physiological component of a sense of justice.

but, Other investigations They repeated these methodologies and did not get the same results. This is common in laboratory studies of animal behavior, because the samples are often small. Without going any further, in the Capuchin study only five females showed repulsion behaviour. For this reason, it is important not to be left alone with the headlines filling the newspapers and to continue investigating the case.

In contrast, there is a great deal of controversy when it comes to explaining the behavior of animals that reject a lesser quality item. Intuitively, we resort to a sense of fairness because we feel limited, but does frustration really arise from comparison with a partner? Or could there be another explanation?

Two opposing hypotheses that seek answers prevail. On the other hand, the adversity in the face of inequality hypothesis advocates the existence of social comparison. that if no other individual was receiving better food for the same work, this behavior would not have occurred.

On the other hand, the hypothesis of social deception raises the question of the meaning of justice in animals. She points out that they do not respond to inequality, but are simply disappointed in a person because they see that they can offer him his favorite food and this is not the case. In other words, frustration is not in social comparison, but in comparing how they are treated in relation to what they could be. Currently, there is evidence that this hypothesis is not misleading. A recent example is the research conducted by researchers from the German Primate Center on macaques. The dynamics of the study were similar to those of the experiment described earlier, with the difference that sometimes it was a machine rather than a human who selected and delivered the food.

Monkeys never refused food when fed by a machine, whereas they would do so over 20% of the time if fed by a human. According to the study authors, these findings support the social deception hypothesis. Monkeys have no social expectations for a machine and therefore cannot be disappointed. Instead, they had a positive relationship with the human who performed the experiment.

This study does not show that animals lack a sense of justice, because the conclusions we can draw in laboratories are always limited. It is in freedom where the behavior of animals is most authentic. However, it sheds light on the debate. Among other things, it invites us to revise the interpretation of the famous 2003 experiment, causing the arguments it uses to defend that monkeys have a sense of justice to lose strength.

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