Family Relationships And Sibling Intelligence

Abstract

The aim of this study was to reveal links between family relationships (parent-child and sibling relationships) and sibling intelligence. 83 two-parent families with two children aged 7‒22 participated in the study. The mean age of elder siblings was 17.59 years (SD = 2.36), the mean age of younger siblings – 14.35 years (SD = 2.66), the mean age of fathers – 45.64 years (SD = 5.64), the mean age of mothers – 43.26 years (SD = 4.27). The age gap between siblings was less than 6 years. To measure siblings’ IQ, the Russian versions of Wechsler Intelligence Scales (WAIS and WISC) were used. Parenting styles were evaluated by the Parent-Child Interaction Questionnaire (five scales), sibling relationships were estimated using the Sibling Inventory of Differential Experience (SIDE) (only the sibling interaction part was used). Student’s t-test, Cohen’s d, Spearman correlation analysis and hierarchical regression analysis were used to analyze the results. It was found that parents exert greater control over younger siblings than their elder brothers or sisters. Elder siblings exhibited more cooperative and dominant behaviors toward the younger ones. On the other hand, younger siblings tended to show more closeness to the elder children. Parental control was negatively associated with intelligence scores of elder and younger siblings. The significant predictors of children’s IQ depended on birth order.