Factors influencing language performance in boys and girls at age 2 in the French ELFE birth cohort

[Display omitted] •6415 two-year-old children from the French Birth cohort ELFE.•24 biological and socio-environmental variables including children’s characteristics, parents’ characteristics abd Relationships between parents and children.•Girls (including those with a low score) outperform boys in a vocabulary test.•Numerous variables are associated with a low score but only two variables differently affect boys and girls: health is better in girls and fathers have more playful interactions with girls.•We conclude that sex is a highly significant variable accounting for the different vocabulary performance in girls and boys. Different environmental and biological variables affect the rhythm of language acquisition in children. A substantial amount of literature has shown that girls overtake boys, at least in the early stages of language acquisition. The goal of this study is to investigate how different factors affect language scores in girls and boys. The parents of 6415 two-year-old French children from the ELFE cohort completed a parental questionnaire assessing language development. Our results show that girls do indeed display higher scores. In order to explore the impact of different variables – such as child characteristics, parental characteristics, the extent to which parents have interactions, such as reading and singing with children – on girls’ and boys’ scores, we tested logistic regressions contrasting children with very low scores with those with average or high scores. We found that sex remained a highly significant explanatory variable. Finally, we analyzed the extent to which there are differences between girls and boys in terms of the variables associated with a low score. Strictly exposed to the same unfavorable factors, girls with very low scores at two years master more words than boys with very low scores. Although different variables are significantly associated with a low score, sex remains a highly significant explanatory variable. Hence, our work contributes significantly to the debated issue of sex/gender influence on language acquisition.