Investigating Proxies for Understanding Trajectories: Heritage Language Maintenance and Child Second Language Acquisition in Refugee Contexts (INPUT) will examine heritage language and child second language development in the European refugee context. INPUT will significantly add to a sub-field of bilingualism studies, Heritage Language Bilingualism (HLB), by studying refugee heritage speakers in Europe, an understudied subset of HLB. This empirical study will investigate linguistic and extra-linguistic variables affecting the development of both the societal majority language and the heritage language with the goal of impacting education policy development. Heritage language Syrian Arabic in Germany and second language German will be investigated with a focus on 6- to 12-year-old children to examine developmental trajectories. The overall research objective is to understand the extent to which increased or reduced heritage language exposure affects heritage language and child second language trajectories and outcomes. For Europe, supporting refugee youth can have significant impact towards the publicly stated goal of integrating this population into their newly adopted countries. One major impediment to this integration is their successful acquisition of the societal majority language while maintaining and developing the first language. Our hypothesis is that support for continued development in the heritage language will improve second language development with knock-on effects for the academic achievement of refugees. At present, heritage language support and training varies tremendously all over Europe. Project findings will be relevant especially for policy makers, teachers, school principals and HLB communities in European countries that have seen a notable increase of Syrian Arabic heritage speakers. To date, most heritage language studies have focused exclusively on the minority language, INPUT helps to fill an important gap by focusing on both languages.