A child's desire to share becomes influenced by social norms around the age of eight, new research has revealed.

The extensive study -- conducted on eight diverse societies across the world -- examined children and adults' behaviour when asked to respond to a set of specific sharing tasks.

Researchers led by Dr Bailey House from the University of York's Department of Psychology established the sharing patterns of adults in the eight societies, and then worked with children from the same communities to determine how they would split a set of rewards in an experimental sharing task.

Children were given a choice between two options: a generous option which delivered one reward to them and one reward to a stranger. The selfish option delivered both rewards to the child.

Children under seven largely opted for the selfish choice, while between eight and 12 children in some societies increasingly shared one of the tokens, as children began to follow the usual adult pattern of behaviour in their community. At about the same age, children in all societies also began to more strongly respond to social norms: they shared more when told that the generous option was "right," and they shared less when they were told that the selfish option was "right."

Dr House said: "These results suggest that during middle childhood children become sensitive to culturally-specific information about how to behave. This "information" may be encoded in local norms, which children acquire through an evolved human psychology for learning and conforming to normative information. This implies that that we ought to have a universally-developing psychology for becoming sensitive to normative information, and that variation in prosocial behaviour ought to be linked to variation in the content of a society's social norms, and not to variation in development."

Dr House studies decision-making and behaviour in adults and children, how these vary across diverse societies, and how they are shaped by both cultural beliefs and evolved adaptations.

For this research, eight different study groups were observed including urban communities in Germany, USA, Argentina and India, as well as rural communities in Ecuador, Vanuatu, and Argentina and hunter-gatherers in Tanzania.

Dr House said: "People in all of these groups share extensively, but they are used to doing so in different situations and probably for different reasons. This is likely why people in these different societies made very different choices when we put them all in the exact same sharing situation.

"One of the implications of the study is that we should start to pay attention not just to what children know but why they start to follow social norms. The next step is to pose the question of what is happening in a child's development between the ages of eight and 12 that makes them more responsive to social norms around them. The goal of the work is to better understand how culture and psychological maturation work together to produce human diversity in cooperation and other behaviours."

Collaborators on the study included Joan B. Silk from Arizona State University, Patricia Kanngiesser from Frei Universität Berlin and Clark Barrett from University of California, Los Angeles.