“…First, no studies that we know of have examined this question in children younger than 21 months of age, even though children can help with simple instrumental tasks as early as 12 months (Sommerville, Schmidt, Yun, & Burns, 2013). Second, in contrast to this demonstration of early prosocial selectivity, studies that measure how likely children are to help a single recipient who was nice or mean to them, rather than forcing them to choose between helping a nice recipient or a mean recipient, suggest that it is not until age 3 that children adjust their prosocial behavior on the basis of how others have treated them (Fujisawa, Kutsukake, & Hasegawa, 2008;Levitt, Weber, Clark, & McDonnell, 1985;Sebastián-Enesco et al, 2013;Warneken & Tomasello, 2013).…”