Having an elder brother is associated with slower language development

Human and social sciences

Several studies had already demonstrated that children who have an elder sibling have poorer linguistic performance than those who have none. Now a research team at the CNRS, Hôpital Robert-Debré AP-HP, the EHESS, the ENS and the INSERM1 has reported a more specific result: this only concerns children who have an elder brother. This work was published on 14 August in Psychological Science.

  • 1These researchers are part of the LSCP Laboratory (CNRS/ENS/EHESS), the Center of Research in Epidemiology and Statistics (INSERM) and the Département de Psychiatrie de l’Enfant et de l’Adolescent at the Hôpital Robert-Debré AP-HP.

Intuitively, it is tempting to think that a child who has an elder brother or sister will grow up in a stimulating linguistic environment and will develop their language skills faster than the family’s firstborn. However, several studies have shown the contrary: the acquisition of language in a child with an elder sibling is reported to be slower than a child who has none.

What is even more surprising is that apparently only elder brothers impact the language skills of their younger siblings, as a study conducted by a research team from the CNRS, the AP-HP, the EHESS, the ENS and the INSERM has just shown. The study finds that children who have grown up with an elder sister have identical development to children with no elder sibling.

More than 1000 children have been followed from birth to five and a half years old in the mother-child cohort EDEN1 . Their language skills were evaluated at 2, 3 and 5.5 years old by tests measuring several aspects of language, such as vocabulary, syntax and verbal reasoning. Children who have an elder brother had on average a two-month delay in language development compared with children with an elder sister.

The scientists propose two hypotheses that may explain this result. The first is that elder sisters, in being more willing to talk to their younger siblings than brothers, may compensate for their parents being less available. Another hypothesis would be that elder sisters compete less than elder brothers for parental attention.

Though this study cannot separate these two hypotheses, it does show that early language development in a younger sibling tends to be slower when the elder is a boy. For their next project, the scientists want to examine the impact of culture (specifically geographical origin) on these results.


Children who have an elder brother have slower linguistic development on average.
© Hugo Peyre


  • 1The EDEN cohort recruited families between 2003 and 2006 in the CHU in Nancy and Poitiers.

The effect of siblings on language development as a function of age difference and sex. Naomi Havron, Franck Ramus, Barbara Heude, Anne Forhan, Alejandrina Cristia and Hugo Peyre. Psychological Science, August 14, 2019.


Franck Ramus
CNRS researcher
Maxime Dos Santos
CNRS press officer