Becoming an older sibling: Introducing the sibling outcome survey (SOS) - an instrument for assessing risk and resilience in the toddler-newborn infant relationship

Children's sibling relationships entail both positive and negative responses. However, previous work has tended to focus on aspects that are negative aspects, while neglecting those which are positive. In addition, much research on sibling relationships has been conducted using children with adequate language skills, thus they fail to address early periods in the development of the sibling-newborn infant relationship. The current chapter presents a study that aimed to overcome these gaps by developing an instrument with items that capture both positive and negative aspects of children as young as 12-months, and their relationships with their newborn infant siblings. It also aimed to capture the progress of children's relationships with their newborn siblings across the first year following the sibling's birth. Data were collected from pregnant mothers and their children prior to the sibling's birth (T1), one month after the birth (T2), and one year later (T3). Exploratory factor analysis was used to validate the existence of positive and negative factors and to select items which loaded on each factor. Preliminary evidence of concurrent and predictive validity of the instrument was established through correlations with established measures of child well-being. We conclude by proposing that this instrument shows promise for use in clinical and research settings which probe the ingredients of successful sibling relationships.