A genetic analysis of differential experiences of adolescent siblings across three years

Environmental factors work to make siblings in the same family different from one another rather than similar. The Sibling Inventory of Differential Experience (SIDE; Daniels & Plomin, 1985) was constructed to evaluate how differently siblings perceive their experiences to be across three domains: parental treatment, sibling treatment, and peer characteristics. The goals of the study were threefold: to assess the degree to which siblings agree about their differential experiences; to examine the stability of perceived differential treatment across three years; and to assess genetic and environmental contributions to the SIDE using both the twin design and the stepfamUy design. These goals were explored using a genetically sensitive sample of 719 samesex sibling pairs ranging from 10 to 18 years of age of whom 94% of eligible pairs were retested three years later. Results indicated moderate agreement between siblings, and considerable stability across 3 years. As in previous research on the SIDE, MZ vs. DZ results indicated greater genetic influence than did results for full siblings vs. genetically unrelated siblings. The results suggest that, although intended as a measure of nonshared environment, the SIDE is not impervious to genetic influence as assessed by the twin design.