Fujii et al. (2016)

Fujii, T.(藤井貴之), Schug, J.(ジョアンナ・シューグ), Nishina, K.(仁科国之), Takahashi, T., Okada, H., & Takagishi, H.(高岸治人)(2016).
Relationship between Salivary Oxytocin Levels and Generosity in Preschoolers.
Scientific Reports, 6: 38662 
doi: 10.1038/srep38662
This study examined the association between salivary oxytocin (sOT) levels and generosity in preschoolers. Fifty preschoolers played two dictator games (DG) by deciding how to allocate 10 chocolates between themselves and another child, who was either from the same class as the participant (ingroup member), or an unknown child from another class (outgroup member). sOT levels were assessed in saliva collected from the children immediately prior to the DG tasks. While sOT levels were negatively associated with allocations made to both ingroup and outgroup members by boys, among girl sOT levels were positively related to allocations made to ingroup members, and unrelated to allocations made to outgroup members. These results suggest sex differences in the association between salivary oxytocin and generosity.