Could you never beat your older brothers and sisters in an argument? Jennifer Jenkins, the Atkinson chair of early childhood development and education at the University of Toronto, suggests that “the larger the family, the less good the child’s skill in language and IQ.”
But there is hope. Jenkins and researchers reviewed an old trial “that included families from Toronto with 385 young children who had a sibling at least four years older.” While younger siblings tended to score lower, those with siblings and mothers who gave positive feedback to the younger child’s abilities tended to score higher. This correlation stayed strong even after traits like gender and age were considered.
Jenkins acknowledges the study’s limitations. She and her colleagues wrote in Pediatrics that it could be “the younger child’s abilities” influencing the “interactions their older siblings have with them” and not the other way around. Nevertheless, Jenkins states that “Siblings really play this very strong role in how kids come out.” So go on and keep arguing with your siblings, just make sure to complement each other when you deserve it.