“It’s not fair”. These are perhaps the most familiar reaction words we hear at all ages, from a child who wants to play football and chooses someone else to take his place, to an adult who learns that a colleague makes more money doing the same job.

People have a strong sense of injustice and complain when they feel it. This feeling is thought to have played a role in the evolution of human cooperation, as monkeys also get angry when they are treated unequally.

One study found distinct signals in monkeys’ brains that show they recognize bias. There is also this humorous, highly publicized video of a monkey throwing cucumber slices back at a researcher after seeing a monkey in a nearby cage pick up grapes to complete the same task.

However, some scholars question whether animals really understand the concept of justice.

A study in Germany showed that long-tailed macaques may not receive the same food from humans and automatons, meaning they can tell the difference and respond.

The study, which was published in the Royal Society Open Science in March, looked at different scenarios: in one, a monkey received fennel from a human, while a monkey next to it received the same food from an automatic dispenser. In another set, the monkey received fennel from a car, while the monkey in an adjacent cage received grapes from a human.

The researchers found that the monkeys were more likely to refuse low-value food than humans, but accepted the same inexpensive food from the car.

According to the analysis, monkeys understood that the goal of man is to provide them with low-quality food. as opposed to a machine that did automated work.

Sarah Brosnan, distinguished university professor of psychology, philosophy, and neuroscience and co-director of the Center for Language Studies at Georgia State University, said the study added another dimension to previous findings.

The fact that the monkeys focused on humans “suggests it’s a social response,” said Brosnan, who was not involved in the German study.

“To use a rough analogy, if someone pays me less than the person next to me for the same job, I will be upset with them, but if the printer makes a mistake and prints a check for less, I won’t feel like it was unfair,” he said.

According to the Washington Post