To share or not to share?

When are primary school children willing to share valuable resources with others and when are they not? A team of researchers from the University of Vienna lead by cognitive biologist Lisa Horn investigated this question in a controlled behavioural experiment. The motivation to share seems to be influenced by group dynamical and physiological factors, whereas friendship between the children seems to be largely irrelevant. The results of their study have been published in the journal "Scientific Reports". In a multipart study the researchers first observed the children's interactions during free play in the classroom setting and further asked the children to name their best friends in the class. Additionally, they recorded a physiological marker for prenatal testosterone. Anthropologists argue that the level of testosterone present during pregnancy leads to a "masculinisation effect" in both men and women, both on a physiological level as well as regarding behavioural strategies. In a controlled behavioural experiment the children then had multiple opportunities to choose between two different distributions of valuable resources, namely glitter stickers: they could choose the egoistic option, in which only they themselves received a sticker, or the prosocial option, which provided a sticker to them as well as to the partner child.