Effects of cumulative language exposure on heritage and majority language skills Spanish and Mandarin heritage speakers in the USA

This study investigated the effects of the amount of cumulative heritage language (HL) exposure during three time periods, on heritage and majority language performance in young adulthood, among two distinct groups of immigrant populations in the USA. Within each time period, exposure from three different sources were examined, and amount of cumulative exposure was calculated encompassing exposure from preceding periods. Factors that may modulate exposure effects were also assessed. Results showed that greater cumulative HL exposure from people at home during all three time periods significantly predicted HL skills for both language groups. For effects on English skills, only the Spanish group showed any influences of exposure. These effects were modulated by parental English proficiency. Input from other sources had less impact. The present findings support the role of parental input throughout childhood, adolescence, and early adulthood in improving HL skills, with less noticeable consequences for the majority language.