Language in good company: unraveling peer effects on language development in early education using integrative data analysis of six German studies

Peers play a central role in children’s learning environments. Nevertheless, the empirical evidence regarding their influence on language development remains inconclusive. This study employed an integrative data analysis (IDA) approach to systematically investigate the effect of peers' average language abilities on individual language development across six German longitudinal studies. The analysis encompassed over 15,000 children (ages 3-10) from more than 2,500 linguistically and socioeconomically diverse preschool and primary school classrooms. In a consistent methodological approach, we estimated peer effects and moderation effects within each data set separately by specifying multilevel regression models, controlling for key individual background variables and peers’ socioeconomic status. These effect sizes were then meta-analytically aggregated. The results demonstrated considerable variability across studies, with no significant aggregated main peer effect. However, a significant interaction between peers' language abilities and a child's prior skill level emerged. Children with lower initial language skills benefited, on average, more from being in classrooms with higher average peer language abilities, while higher skilled children's development was less affected by their peers. By employing IDA with meta-analytic aggregation, the study offers overarching conclusions that extend beyond the scope of individual studies, contributing to a more nuanced understanding of peer influences on language development across diverse educational settings. The findings underscore the crucial role of peers in shaping language development trajectories and suggest that considering peer effects in educational strategies and thoughtful classroom composition could enhance language development opportunities, especially for less skilled children.