Sibling Influences on Prosociality

Siblings are often overlooked as a source of social influence. Addressing this gap, we review findings from studies spanning the transition to siblinghood through adolescence. We have identified four features of sibling relationships that help explain siblings’ powerful influence on children’s prosocial behavior: sibling relationships are (1) emotionally unfettered; (2) diagonal, especially in the early years; (3) familiar; and (4) long-lasting. Research is framed by several distinct theoretical perspectives, including attachment theory, ethology, family systems theory, and cognitive accounts of theory of mind development. Sibling influences also take many forms that vary in salience across the different aspects of prosocial behavior and distinct developmental periods. Over time, sibling influences show both stability and change, but appear independent from parental influences – although evidence is scarce for some groups. Finally, we discuss future directions, as well as conclusions regarding the nature, motivation, and impact of sibling influences on prosocial behavior.