Psychologists at Jena University say that prejudices within children are “quite normal.”

"Approximately at the age of three to four years children start to prefer children of the same sex, and later the same ethnic group or nationality," Prof. Dr. Andreas Beelmann of the Friedrich Schiller University Jena (Germany) states.

Beelmann explained that this is an entirely normal personality development.

"It only gets problematic when the more positive evaluation of the own social group, which is adopted automatically in the course of identity formation, at some point reverts into bias and discrimination against others," said Beelmann in a study published in Child Development.

The psychologists are working on a prevention program for children to reduce prejudices between them and to encourage tolerance for others.

The findings showed that the development of prejudice increases steadily at pre-school age, reaches the highest level between five and seven year olds, and declines with increasing ages.

"This reflects normal cognitive development of children," Beelmann explains.

"At first they adopt the social categories from their social environment, mainly the parents. Then they start to build up their own social identity according to social groups, before they finally learn to differentiate and individual evaluations of others will prevail over stereotypes."

Because of this time frame in connection with prejudices the psychologists suggest that this age is the best time to start prevention programs against prejudices.

"Prevention starting at that age supports the normal course of development," said Beelmann.

While they found that prevention programs reduce the prejudices at primary school age they said that this also works when “when they don't even get in touch with real people but learn it instead via books or told stories."

"If there is no or only a few contact to members of social out groups, there is no personal experience to be made and generalizing negative evaluations stick longer,” according to a statement from the University.

While the children and youth attitudes towards different social groups can be changed at an older age, the researchers suggest that the changes begin at an early stage to “less depend on the individual development and very much more on the social environment”

"People who can identify with many groups will be less inclined to make sweeping generalizations in the evaluation of individuals belonging to different social groups or even to discriminate against them.”