Differential experiences of siblings in the same family as predictors of adolescent sibling personality differences.

In the area of personality development, environmental influences operate to make siblings in the same family different rather than similar to each other. The goal of the present study was to determine whether differential experience of siblings can be used to explain the marked personality differences of siblings. The Sibling Inventory of Differential Experience (SIDE) along with personality information (the EAS Temperament Inventory and questions about career expectations) was administered to 50 biological sibling pairs and 98 adoptive sibling pairs in adolescence and young adulthood. The results indicated that differential sibling interaction and differential peer characteristics as self-reported on the SIDE explain 6%-26% of the variance in sibling personality difference scores. For example, the sibling who reports more sociability as compared to his sibling also experiences more sibling closeness and more peer popularity as compared to his sibling. Comparison between adoptive and biological siblings indicates that the SIDE relations are mediated environmentally rather than genetically.