Although the scientific community is still searching for a defining characteristic of developmental language disorder (DLD), problems with subject-verb agreement, and by extension morphosyntax, have been identified as a hallmark of English-speaking preschoolers and older children with DLD. However, in studies of French-speaking preschoolers with DLD, morphosyntax has not been found to be a specific linguistic weakness. Since there is evidence that some aspects of morphosyntax in French are acquired by children with typical language (TL) development only later in childhood, such as subregular and irregular subject-verb number agreement, henceforth SUBIRR, morphosyntax has been argued to be a French marker for DLD only in older childhood and adolescence. The present thesis aimed to determine if French speaking (pre-)teenagers with TL have acquired SUBIRR number agreement, resolve whether French-speaking (pre-)teenagers with DLD are impaired on SUBIRR number agreement, and establish whether morphosyntax is an area of weakness as compared to lexico-semantics in this population. SUBIRR number agreement and morphosyntactic skills were evaluated with tasks targeting the behavioural and neurocognitive levels using linguistics tasks and event-related potentials (ERP). Furthermore, we contrasted two theories' predictions on morphosyntactic skills in (pre-)teens with DLD : the procedural deficit hypothesis (Ullman & Pierpont, 2005; Ullman et al., 2020), and the generalized slowing hypothesis (Kail, 1994). This thesis is composed of three manuscripts for publication. The first evaluated our participants' skills in multiple linguistic domains with behavioural tasks typical of clinical and research settings. Data reveal impairments in the DLD group in both lexico-semantic and morphosyntactic domains but suggest that a SUBIRR number agreement task was best at discriminating DLD from controls. The second article presents a novel ERP experimental design using only grammatical sentences, presented simultaneously with semantically and grammatically congruent or incongruent images, to assess morphosyntactic and lexico-semantic sentence processing at the neurocognitive level. Data from twenty-eight French-speaking adults show that they elicited the expected ERP components found in previous studies using ungrammatical sentences. These data served as a reference to establish whether our participants with and without TL process sentences in a mature way. The third article tested this novel ERP experiment with our (pre-)teen participants. We tested predictions of the procedural deficit hypothesis which states that children with DLD should have impaired morphosyntax due to an underlying procedural memory deficit, and the generalized slowing hypothesis, which proposes that all linguistic domains should be impaired due to an underlying processing deficit. This experimental design was run on teens with and without DLD. Although some processing delays were found in the DLD group, results on most conditions better fit the procedural deficit hypothesis. This study suggests that, in contrast with morphosyntax, lexico-semantics is a relative strength in teenagers with DLD when processing linguistic information at the neurocognitive level. Overall, this thesis reveals that morphosyntax, tested through SUBIRR number agreement, is especially impaired in French-speaking teens with DLD when compared to their TL peers. We discuss the findings in relation to clinical practice and highlight the importance of examining neurocognitive processes in language assessment.

The Routledge Handbook of Experimental Linguistics provides an up-to-date and accessible overview of various ways in which experiments are used across all domains of linguistics and surveys the range of state-of-the-art methods that can be applied to analyse the language of populations with a wide range of linguistic profiles. Each chapter provides a step-by-step introduction to theoretical and methodological challenges and critically presents a wide range of studies in various domains of experimental linguistics. This handbook: Provides a unified perspective on the data, methods and findings stemming from all experimental research in linguistics Covers many different subfields of linguistics, including argumentation theory, discourse studies and typology Provides an introduction to classical as well as new methods to conduct experiments such as eye tracking and brain imaging Features a range of internationally renowned academics Shows how experimental research can be used to study populations with various linguistic profiles, including young children, people with linguistic impairments, older adults, language learners and bilingual speakers Providing readers with a wealth of theoretical and practical information in order to guide them in designing methodologically sound linguistic experiments, this handbook is essential reading for scholars and students researching in all areas of linguistics.

This collection of papers by leading psychologists includes ground-breaking research on the similarities between SLI and autism, plus other studies at the cutting edge of the field of language impairment and developmental disorders.

Children with Specific Language Impairment covers all aspects of SLI, including its history, possible genetic and neurobiological origins, and clinical and educational practice.