A team of researchers affiliated with the Max Planck Institute for Evolutionary Anthropology, Yale University and the University of Göttingen, has found that older children are more likely to make seemingly irrational decisions when social comparison is at play. In their paper published in Proceedings of the Royal Society B: Biological Sciences, the group describes experiments they carried out with chimps and children of various ages and what they found.
To better understand how social comparison works in humans, the researchers designed an experiment to test the differences between chimpanzees, young children and older children.
The experiment involved 96 children between the ages of five and ten, and 15 adult chimpanzees. The subjects chose between two trays of treats as they sat opposite one of their peers. But the trays all came with a set of conditions—treats had to be shared in a certain way. One type of tray would have three treats, the other tray nine. If the child chose the tray with three treats, he or she would get to keep two, while their peer got one. If, on the other hand, they chose the tray with nine treats, they would get three of them, while their peer would get six.
The researchers report that the vast majority of the chimpanzees and children under six chose the tray with more treats on it. Those children over six tended to choose the tray with fewer treats on it.
The researchers suggest their results show an example of irrational thinking by older children due to social comparison. All of the children (and the chimps too), regardless of age, knew that they would get more treats (three instead of one) if they chose the tray with nine treats on it. Thus, the logical choice was to pick that one. But the older children were more concerned about fair play. They did not like the idea of their peer getting more than them, even if they themselves got less than they could have if they had only chosen the tray with more treats on it.
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Esther Herrmann et al. Human children but not chimpanzees make irrational decisions driven by social comparison, Proceedings of the Royal Society B: Biological Sciences (2019). DOI: 10.1098/rspb.2018.2228