An IP-related Syntactic Developmental Sequence (ISDS)

The purpose of this study is to explore the question on how we can establish an IPrelated syntactic developmental sequence. For a possible answer to this question, this study proposes an IP-related Syntactic Developmental Sequence (ISDS) derived from the Syntactic Developmental Sequence (Kim, 2006; Vainikka & Young-Scholten, 1998). The ISDS constitutes an implicational developmental sequence of the Single IP-the Double IP-the Multiple IP Stage in terms of the number of the auxiliary verbs in a sentence. The Single IP Stages follow an implicational sequence of Underspecified IP→TP→AgrP stage in terms of the LC in accordance with the Split-IP hypothesis. The Double IP Stages also follow an implicational sequence of Underspecified IP→ModP→AuxP*→TP→AgrP→ForP stage in terms of the LC in accordance with the Split-AuxP hypothesis. The Multiple Stages are involved in the operations of modand aux-matching mechanisms which govern the matching of the aux-features and the mod-features, and the agreeing of modality, aspect, and passive features. Then, this study demonstrates that each stage of the ISDS can be examined on the IL data from sequence-based SLA research. In conclusion, the ISDS can determine the syntactic IL developmental sequence for the Double or the Multiple IP Stages as well as the Single Stages, and hence provide a theoretical framework for UG-based SLA research.