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Prejudice in humans has ancient evolutionary roots

The tendency to perceive others as "us versus them" is not exclusive to humans, but also exists in some of our cousins ​​- the primates. This is according to a new study led by researchers at Yale University and with the participation of Prof. Gil Dizandrok from the Department of Psychology and the Gonda Center for Brain Research at Bar-Ilan University and researchers from Harvard University

Rhesus monkeys. show flexibility in choosing their friends. Photo: Yale University
Rhesus monkeys. show flexibility in choosing their friends. Photo: Yale University

The tendency to perceive others as "us versus them" is not exclusive to humans, but also exists in some of our cousins ​​- the primates. This is according to a new study led by researchers at Yale University and with the participation of Prof. Gil Dizandrok from the Department of Psychology and the Gunda Center for Brain Research at Bar-Ilan University and researchers from Harvard University.

In a series of experiments, researchers led by psychologist Lori Santos showed that monkeys treat individuals outside their group with the same suspicion and resentment that humans tend to attribute to strangers, suggesting that the conflict between the different human groups has strong evolutionary roots. The findings were reported in the March issue of the Journal of Personality and Social Psychology.

"One of the more troubling aspects of human nature is that we evaluate people differently depending on whether they are our 'ingroup' friends or 'outgroup' strangers," Santos said. "To a large extent all conflicts in human history have involved people discriminating based on who they share in race, religion, social class, etc. The question we were interested in, where do these diagnoses come from?"

The answer, she adds, is that such biases have probably been shaped by 25 million years of evolution and not just by human culture.

Santos and the people in her lab studied the rhesus monkeys living on an island off the coast of Puerto Rico. Like humans, monkeys in this population naturally live in different social groups based on family history. To assess whether monkeys made the distinction between individuals in the same ingroup and between outgroup strangers, the researchers used the well-known tendency of animals to look longer at new or fearful things than at familiar or friendly things. They presented the monkeys, side by side, pictures of monkeys that were from their own social group or members of another group. They found that the monkeys stared longer at pictures of other monkeys that were outside their group, suggesting that the monkeys spontaneously recognize who is a stranger and who is a member of their group.

"What made this result even more impressive," noted Neha Mahajan, a PhD student at Yale University who led this project, "is that monkeys in the population move from group to group, so some of the monkeys that were strangers were previously members of the same monkey's group, but Even so, the results are significant even for monkeys that moved from group to group just a few weeks earlier. This indicates that these monkeys are sensitive to the members of their current group. In other words, even if the monkeys divide the world into 'us' and 'them', they do so flexibly and update their decisions in real time."


Santos and her colleagues then asked whether monkeys evaluate members of a group and members of other groups in a different way, i.e. do they associate them with "good" and "bad" respectively? They developed a monkey version of the hidden attitudes test (IAT) that is usually done on humans. In humans the test measures the degree of bias of humans towards members of other groups. To test the same feature in monkeys, the researchers showed the monkeys a sequence of pictures in which the pictures of members of their group and of monkeys from other groups appeared in pairs together with good things such as fruit or bad things such as spiders.

The researchers measured the amount of time the monkeys stared at the two types of image sequences. It turned out that they stared longer at their non-constant value image sequences than constant value sequences. For example, he stared more at a sequence consisting of pictures of other-group monkeys (negative) and fruits (positive) than at a sequence of other-group monkeys and spiders (both negative). Like humans, monkeys spontaneously tend to see members of their group as good and members outside their group negatively.

"Because both humans and rhesus monkeys make distinctions between 'us' and them, the roots of prejudice in humans originate 25 million years back when humans and rhesus monkeys share a common ancestor."

Social psychologists introduced to the world the idea that the immediate situation has a huge influence in determining behavior, including intergroup feelings, says Mehazarin Banjai from the Department of Psychology at Harvard University and a co-author of the article. "The evolutionary theories make us aware of our past. In this work we connect the years and show the importance of both influences in this work."

"The bad news is that the tendency to hate members of other groups has an evolutionary history, and will therefore be less straightforward to reverse than we would like to think." Santos said. "The good news is that even monkeys are flexible about their group members. If humans find ways to take advantage of this flexibility, it may make us a more tolerant species."

Dizendrock does build on this potential flexibility, and for years has been conducting research on the development of Israeli children's views on in-groups and out-groups. His research shows that from an early age secular and religious Jewish children, and Arab children demonstrate a belief that the two nationalities are fundamentally different from each other, and that this cannot be changed.

Recently, Dizandrok started an innovative study in his laboratory at the Gonda Center for Brain Research at Bar-Ilan University, where he and a team of students are trying to test the process of creating social groups in 9-11 month old babies. Those interested in hearing more about it, or participating in research, Welcome to visit the site.

14 תגובות

  1. correct:
    It's a shame to waste your time, but as I said - all opinions are prejudiced and the existence of a "prejudicial" opinion does not, therefore, indicate any flaw in the opinion.
    You understand?
    No, but it did.
    Of the opinions, which are all preconceived, there are some (mine, for example) that are the result of critical and logical thinking and there are some (for example yours) that are the result of brainwashing and lack of thought.

    It is true that it is customary to use the expression "prejudices", but this is not intended to indicate the fact that the opinions are prejudiced, but rather that the conclusion drawn from them is drawn based on them alone while unjustifiably ignoring the data on which the same opinion was used.
    This is very appropriate for the behavior of religious people whose views were planted in their minds through brainwashing when they were still babies and they don't let the facts confuse them.

    You, for example, completely ignore the fact that my father simply translated an article on evolution here and did not express any opinion of his own, and start talking about his prejudices and his origin.
    Based on this behavior of yours, I have already formed an opinion about you (which is now already prejudiced) that your prejudices do function as prejudices for you.

  2. Mr. Rothschild
    It follows from your words that anyone who thinks that 1+1 equals 2 is prejudiced.
    So what is the difference between belief in logic and prejudice in your opinion.

  3. correct:
    You have a prejudice against the author of the article, so we can guess what your opinion is.

    All the opinions in the world are ancient and the person whose opinions will actually be future has not yet been born.
    The question about opinions is not whether they are prejudiced but whether they are correct.
    It is evident that your views are incorrect.

  4. The author of the article is prejudiced against the religious
    Therefore we can deduce his origin from this.

  5. Year:
    It seems to me that you are ignoring some of the findings.
    One of the experiments showed exactly the connection that the monkeys make between "good" and "member of the group" and between "bad" and "one who is not a member of the group".
    It's not a matter of "familiar" versus "unfamiliar"

  6. So if it is genetic and we are all racist then why is it so politically incorrect today to be a national patriot?

  7. The article is full of unproven bombastic claims.
    What he proves is nothing but that there are similar patterns of perception for monkeys and humans.
    The claims about evolutionary roots for prejudice are not proven at all, and the findings can be interpreted just as well as a distinction between the familiar and the unfamiliar or less familiar.
    The claims about a tendency to hate the stranger that is supposedly shared by monkeys and humans do not deal with countless cases of friendly reception of strangers.

  8. Primates have a common ancestor with humans. It's not cousins ​​and it's not them themselves or their ancestors who were in the chain of evolution that led to modern humans (homospecians).

  9. A delusional experience as an example..
    In Scouts in the XNUMXth grade, I was in a group made up of two classes from the same school.
    A year later they wanted to join a group from another school.
    One of the trainees was so locked in on the issue of them and us.. that he was not ready to accept the possibility of merging a group from two different schools (Shomo Shimayim) while the members of my original group had already "experienced a merger. It was easier..

    In my opinion this proves that it is in human nature regardless of "logic" but rather it is more emotional.
    It is possible to practice this and thereby communicate the understandable reluctance...

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