Sibling differentiation in activity interests: Longitudinal linkages to sibling relationship quality and self-worth
Open Access
- Author:
- Doughty, Susan Elizabeth
- Graduate Program:
- Human Development and Family Studies
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- July 28, 2015
- Committee Members:
- Susan Marie Mc Hale, Dissertation Advisor/Co-Advisor
Mark E Feinberg, Committee Member
Gregory M Fosco, Committee Member
D Wayne Osgood, Committee Member - Keywords:
- sibling relationships
homophily
deidentification
activity interests
self-worth - Abstract:
- Although the emergence of sibling differences has long been a subject of interest, little empirical work has examined the development of sibling differentiation over time, or the ways in which sibling differentiation is linked to relational and individual outcomes. This study focused on sibling differences in self-rated activity interests (e.g., the extent to which siblings differ in their level of interest in sports, reading, hobbies, etc.), with the goal of examining associations between sibling differentiation and both sibling relationship quality and youths’ self-worth over time. Specifically, this study addressed the following research aims: (1) to describe the trajectory of sibling differentiation from middle childhood through adolescence, (2) to assess linkages between sibling differentiation and sibling intimacy and conflict, and (3) to assess linkages between sibling differentiation and youths’ self-worth. I began by charting the developmental trajectory of differences between siblings’ self-reported activity interests from middle childhood through late adolescence. Based on deidentification theory and existing work in behavioral genetics, it was anticipated that siblings would become increasingly different over time. Sibling dyad gender constellation was also examined as a potential moderator of change patterns, given its importance to sibling differences from both the deidentification and behavioral-genetic perspectives. Multi-level modeling (MLM) was then used to examine the longitudinal linkages between differentiation in siblings’ activity interests and their reports of sibling intimacy and conflict. Existing perspectives offer conflicting hypotheses: grounded in Adler’s ideas about the family context of individual development, deidentification theory holds that becoming more different will reduce rivalry and conflict between siblings, allowing for a more harmonious relationship. Principles of homophily suggest the opposite—that the more siblings have in common, the more likely they will be to report close relationships with one another. Sibling dyad gender constellation and birth order were also examined as potential moderators of change patterns, given their relevance to sibling relationship dynamics. To address the third aim, MLM was used to assess linkages between sibling differences in activity interests and a measure of siblings’ individual adjustment—self-worth. Here again, there are competing predictions: deidentification theory predicts that greater differentiation will be linked with positive self-worth. Self-affirmation theory, however, predicts the opposite, as similarity between siblings serves as a source of personal validation and self-worth. Sibling dyad gender constellation was included as a potential moderator of change patterns, given its potential relevance to sibling differentiation. Results for Aim 1 revealed a negative quadratic effect that was qualified by a significant cubic effect for sibling differentiation over time: Sibling differences increased in early adolescence, leveled off, and then increased again in late adolescence--findings that generally support both deidentification and behavioral genetics perspectives. A significant linear by gender constellation interaction also emerged, with follow ups showing that mixed-sex sibling dyads, but not same sex dyads, showed linear increases in differentiation over time. For Aim 2, support was found for principles of homophily. At the within-family level, at times when sibling dyads were more different than their average, youths reported lower levels of intimacy. A similar effect was also found at the between-family level, as youths from families with higher than average levels of sibling differences reported lower levels of intimacy. No association was found between sibling differentiation and sibling conflict, although some significant interactions were found between linear age and both birth order and gender constellation. With respect to Aim 3, support was found for self-affirmation theory: sibling similarity was linked positively to self-worth at the between-family level, such that youths from families with higher than average levels of sibling differences reported lower levels of self-worth. Further, at the within-family level (dyads across time), a significant interaction with gender constellation emerged, indicating that youths from same-sex sibling dyads reported lower levels of self-worth at times when sibling differences were higher their cross-time average—an effect not seen in youths from mixed-sex sibling dyads. Discussion focuses on implications of the findings for theories of sibling influence and directions for future study.