A Four-Year Longitudinal Comparative Study on the Lexicon Development of Russian and Turkish Heritage Speakers in Germany

Russian and Turkish are the most frequently spoken intensively investigated heritage languages in Germany, but contrastive research on their development early childhood is still missing. This longitudinal study compares trajectories of expressive lexicon (n = 70) 79) speakers identifies predictors for size at preschool age. Heritage was tested with two comparable tests assessing four test points between mean ages 3.3 (range: 25–49 months) 5.6 54–78 years. The influence language-related factors, such as input quantity, parents’ language proficiency age onset (AoO) German, other potential predictors, i.e., intelligence socio-economic status, evaluated. Results show that group’s abilities grow slower similar last point. Common quantity from siblings AoO. Group-specific influences parental group siblings’ group. Our findings emphasize interplay society AoO development. relevance our results usage-based theory acquisition discussed.