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 & Plomain, 1985) was constructed to evaluate how differently siblings perceive their experiences to be accross three domains: parental treatment: to assess the degree to which siblings agree about their differential experiences; to examine the stability of perceived differential treatment accross three years; and to assess genetic and environmental contributions to th SIDE using both the twin design and the stepfamily design. These goals were explored using a genetically sensitive sample of 719 same-sex 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 accross 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.