They grow up in the same home, eat the same food, share the same genes (and sometimes the same jeans), but somehow siblings are often no more similar than complete strangers.
A new study from Brigham Young University in the US state of Utah, found that parents’ beliefs about their children — and the comparisons they make — may cause differences to be magnified.
"Parents’ beliefs about their children, not just their actual parenting, may influence who their children become," said BYU professor and lead author of the study Alex Jensen.
The study, published Friday in the Journal of Family Psychology, focused on siblings and academic achievement.
Jensen and co-author Susan McHale from Penn State looked at 388 teenage first and second-born siblings and their parents from 17 school districts.
They asked the parents which sibling was better in school. The majority of parents thought that the firstborn was better, although on average siblings' achievement was pretty similar.
Parents’ beliefs about sibling differences weren’t influenced by past grades, but future grades of teenagers were influenced by parents’ beliefs. The child parents believed was smarter tended to do better in the future.
The child parents believed was less capable tended to do relatively poorer. Specifically, that belief translated to a 0.21 difference in GPA among study participants, reports the university website.
"That may not sound like much. But over time those small effects have the potential to turn into siblings who are quite different from one another."
A parent may think that the oldest sibling is smarter because at any given time they are doing more complicated subjects in school, Jensen said. But when the siblings are teenagers it leads to more differences among them. Ultimately, the 'less smart sibling' will tend to do worse in comparison."
The one exception was when the firstborn was a brother and the second born a sister. In that case, parents believed the sister was more academically competent.
"It’s hard for parents to not notice or think about differences between their children, it’s only natural," Jensen said. "But to help all children succeed, parents should focus on recognizing the strengths of each of their children and be careful about vocally making comparisons in front of them."
