[Acquisition of German morphosyntax in the context of constituent movement into the complementizer phrase position].

German is a genuine verb-second (V2) language. For V2 languages it is assumed that all sentence structures can be derived from the underlying subordinate clause structure via the movement of individual components. The acquisition of German V2 structures represents a critical step in German first language acquisition and is usually mastered at the age of 3 years. However, not all children succeed in filtering the necessary information from the spoken input in order to acquire this key component of German syntax. Use of canonical sentence structures alone is not a confirmation of a successful V2 acquisition. Moreover, this structure often represents some kind of interim grammar. Only the use of complementizer phrase (CP)-related structures, such as wh-questions or topicalizations of objects is a real indication of a successful V2 acquisition.