Supplementary material from "“Help and you shall be happy!”: A longitudinal analysis of preschool-aged children’s happiness after prosocial action"

A growing number of studies suggest that prosocial acts elicit positive emotions in young children (Aknin et al., 2012b; Hepach et al., 2017b; Song et al., 2020). However, prior work has only been cross-sectional and focused on one type of prosocial behavior. Recognising that prosocial behaviour is diverse and develops rapidly throughout the preschool years, the current longitudinal study examined happiness after instrumental helping, comforting, and sharing in children when they were 2- (n = 200), 3- (n = 161), and 4- (n = 135) years-old . Results revealed that children who engaged in prosocial action without being prompted to do so showed the highest happiness with happiness being specific to timepoint and type of prosocial task. To our knowledge this is the first longitudinal study investigating positive emotions as a mechanism underlying prosocial development.