The project aims to advance theoretical and practical knowledge in psycholinguistics and developmental neuroscience, focusing on symptoms of Developmental Language Disorder (DLD). Specifically, I will investigate underlying cognitive factors of syntactic difficulties manifested by children with DLD. I will test the project's hypotheses regarding the inflexibility of statistical learning of syntactic structures in DLD. To this end, I will examine the production and comprehension of relative clauses (RCs) in Italian- and Polish-speaking children with DLD. The RC is a subordinate clause that exhibits different syntactic structures in Italian and Polish. Therefore, the cross-linguistic study will provide a quantitative analysis of local linguistic elements that signify thematic role assignments in RCs and distinguish between Italian (IT) and Polish (PL). Additionally, I will analyze the global RC sentence structure, including length, complexity, and the distance related to syntactic movement. This linguistic analysis will further allow testing of the hypothesis that basic cognitive components and their interactions contribute to the errors typical for children with DLD. Specifically, based on linguistic analysis, I will test neuropsychological hypotheses that the following cognitive elements contribute to DLD deficits: i) executive control, triggered by the probabilistic properties of word/morpheme flow within the sentence; ii) performance in encoding rare linguistic elements, as reflected in inflectional suffixes; iii) working memory load, related to sentence length and syntactic movement. The achievement of the project's aims will impact the international research community by providing new insights into the cognitive aspects of language skills, particularly the development of specific grammatical-syntactic constructions. Finally, the results of the project will be relevant to clinicians in designing targeted, more effective therapeutic programs for children with DLD.