The Acquisition of Syntactic Structures in Typical and Atypical Language Development: Insights from Growing Trees and Syntactic Cartography in a New Sentence Repetition Task

This study presents a newly developed Sentence Repetition Task/SRT as a tool designed to investigate the acquisition of different syntactic structures in children with typical development (TD) and Developmental Language Disorder (DLD). The tool is grounded in the Growing Trees (GT, henceforth) approach, which assumes that developmental progression reflects the hierarchical growth of the syntactic tree, as described in cartographic analyses of clause structure. The SRT Protocol was constructed following the three developmental stages identified by GT: VP/TP, lower zone of the Left Periphery (LP henceforth), and higher LP zone. A preliminary pilot version was administered to 27 TD and 28 DLD children, followed by a revised second version with improved item design and broader syntactic coverage, administered to 28 TD and 21 DLD children. Descriptive and inferential analyses demonstrate a clear hierarchy in the acquisition of Italian morphosyntax, fully consistent with the three-stage developmental progression predicted by the model. Children with DLD follow the same path but with delayed acquisition and slower consolidation of certain structures. These findings provide developmentally grounded benchmarks for identifying morphosyntactic delays and show that the SRT Protocol is a reliable tool for profiling early syntactic development. Crucially, the protocol supports diagnosis and clinical practice by helping clinicians ensuring interventions that are both theoretically informed and aligned with syntactic growth.