Anyone who has been to a school or a workplace probably knows that it is part of human nature to form groups with others. In most cases, groups or cliques are formed on the basis of friendship. Having certain things in common with other members is usually the criteria for admission.
So, some researchers wanted to experiment with that idea. In a study that was conducted to observe the effects of labeling on attitudes, children from 3-5 years of age were tested for their classification skills and self-esteem. The results were then used to ensure that the composition of the "red" and "blue" groups was random.
Teachers then began to implement the results by labeling children and organizing classroom activity accordingly. At the same time, there were control classrooms in which teachers ignored the results completely.
The results? As expected, children in classrooms who had differentiated between "red" and "blue" showed greater in-group bias on various measures than their counterparts in the controlled classrooms.
At any rate, it may be a bit alarming to see how reluctant even children can be to be inclusive when they are taught to distinguish between the "insiders" and the "others" in social settings. That's especially true when there is no discernible difference between the two groups, except for an arbitrary classification as either "red" or "blue."