Gross Motor Development and Birth Order Effects in Large Families

Abstract

This research aims to clarify the relationship between the achievement of gross motor milestones (turning over, sitting up, crawling, standing and walking) in infancy, and birth-order in large families (five or more children). The study also addresses many factors that may influence a child’s development. It was hypothesized that younger children born to large families would achieve their motor milestones at younger ages than their older siblings, that a larger age difference between sibling pairs would be inversely correlated with the younger child’s achievement of motor milestones, that the effects would be stronger if an older sibling is a female than if the older sibling is a male, and that although other factors influence the achievement of gross motor milestones, the older sibling’s age of achievement will prove to be the most significant predictor. The study was conducted on 29 sibling pairs within the Orthodox Jewish population in Israel. A parental questionnaire was administered to assess the development rates as well as other familial characteristics for each sibling pair. Results showed that birth order tends to be a hindering factor in that younger children were consistently later in achieving their motor milestones compared to their own older siblings. Relationships between the age gap and gender of the older child were not significant in this sample. Finally, results suggest that older siblings achievements are the best predictor of their younger sibling’s development. This study provides additional data to the sparse existing literature on the relationships between known factors effecting infant development and how they play out in large families.