Speed of processing in Developmental Language Disorder (DLD): The case of real-time grammatical processing

Background Developmental Language Disorder (DLD) impacts various aspects of children's language abilities, including the processing of inflectional morphology. Prior research suggests that children with DLD exhibit deficits in processing speed and sensitivity to grammatical inflections, yet the relationship between these deficits remains unclear. Aims This study aimed to investigate the relationship between processing speed and sensitivity to inflectional morphology in children with DLD, focusing on their real-time processing abilities in response to regular past tense, third person singular, and regular plural inflections at different rates of sentence articulation. Method Eighteen children with DLD and 18 age-matched controls underwent word monitoring tasks that assessed sensitivity to grammaticality of inflections in sentences presented at normal and slow rates of articulation. Results At a normal rate of articulation, children with DLD demonstrated slower response times and reduced sensitivity to grammaticality across all inflections compared to controls. When the articulation rate was slowed, children with DLD showed improved sensitivity, particularly to regular plural and third person singular inflections, although deficits in processing the regular past tense persisted. Conclusions The findings suggest a significant relationship between processing speed and inflectional morphology sensitivity in children with DLD. Slower articulation rates improved grammatical sensitivity for certain inflections, highlighting the potential of tailored interventions that consider processing speed limitations. Persistent difficulties with the regular past tense inflection indicate the need for targeted support for children with DLD in this area. WHAT THIS PAPER ADDS What is already known on this subject Children with Developmental Language Disorder (DLD) have a wide range of language difficulties, but deficits in inflectional morphology are regarded as a ‘hallmark’ of the disorder. Children with DLD are also very likely to show deficits in speed of processing, although it is not known if a ‘slowness to process’ can causally explain the language difficulties these children experience. What this study adds to existing knowledge When grammatical sensitivity was measured using an online real-time task, children with DLD showed widespread inflectional deficits when sentences were spoken at a normal conversational rate. When sentence articulation rate was slowed down, children with DLD were faster, more accurate and more sensitive to the grammaticality of constructions. However, deficits in the regular past tense remained persistent, even in this slow-rate condition. What are the clinical implications of this work? This study has implications for clinical and educational practices that work with children with DLD to improve their language skills. The findings of this study show that when children with DLD are given more time to process incoming information, their grammatical skills significantly improve. This study also shows that deficits in the regular past tense are persistent, and children are likely need extensive and intensive support with this particular grammatical feature.