Ultimate attainment in bilingual first language acquisition

•Instances of Core-Parameters, Sub-Case-Parameters and Peripheral Variation.•OV–VO Core-Parameter, Null-Subject Sub-Case-Parameter, German Gender Peripheral.•24 German–Romance (French, Spanish, Italian) bilingual children, longitudinal data.•Input, language balance irrelevant for Core-Parameters and Sub-Case-Parameters.•Incomplete acquisition possible for Peripheral Variation.

Montrul, 2008 and Montrul, 2011 has recently argued that heritage languages are acquired incompletely. The present study analyzes longitudinal data of 24 German–Romance and Romance–Romance (French, Italian, Spanish) simultaneous bilingual children until the age of 4 or 5 who have been raised in otherwise monolingual countries where the native language of one parent is not supported by society. In contrast to heritage speakers, the simultaneous bilingual subjects of the present study are exposed to both of their languages at home, i.e. they have native parents of the respective languages. Notwithstanding, these 2L1 children find themselves in a similar situation as heritage speakers since they receive less input in the language which is not supported by society. Less input refers to the number of people who interact with the child in the non-community language and to the hours exposed to the non-community language per day or week.The present article looks more closely at three grammatical domains that are systematically different in the respective languages of the bilingual child and which can be analyzed as belonging to one of the variation forms according to Uriagereka (2007). He proposes instances of three deeper forms of variation: Core-Parameters, Sub-Case-Parameters and Peripheral Variation. We take the Head-Complement Parameter (OV in German, VO in Romance) as a Core-Parameter. As a Sub-Case-Parameter we use the Null-Subject Parameter and as the Peripheral Variation we analyze dative case/gender marking in German. The discussions of the two types of parameters in relation to the observations from 2L1 children support the idea of the existence of a concept such as that of parameters and thus also contribute to the debate against a parametric approach to language variation from the perspective of bilingual first language acquisition.The simultaneous bilingual children have to acquire variation in not just one language, but in both of their languages. We will show that in the cases of Core-Parameters and Sub-Case-Parameters neither the amount of input which the bilingual child receives nor the language (im-)balance measured in the bilingual child has an influence on the setting of the parameter and that the acquisition process is complete, i.e. adult-like by the age of 5. In contrast, language (im)balance does matter in the third case, the Peripheral Variation, and incomplete acquisition may arise, depending on the proficiency level in the respective language. However, the peripheral grammatical domains are also problematic in monolingual acquisition. The main purpose of the article is to take the term ‘incomplete acquisition’ seriously and to raise doubts about incomplete acquisition processes when it comes to variation covered by Core- and Sub-Case-Parameters. Furthermore, if ‘incomplete acquisition’ is observed with peripheral grammatical phenomena, this is so in bilingual and monolingual individuals.