The grammaticality judgement of inflectional morphology in children with and without Developmental Language Disorder.

To explore the clinical potential of grammaticality judgement tasks, this study investigated whether a Grammaticality Judgment Task (GJT) of inflectional morphology could differentiate between a clinically selected sample of children with DLD and children in mainstream (i.e. regular education) schools. We also explored the relationship between grammaticality judgement and measures of receptive vocabulary, receptive grammar, and nonword repetition. Children with DLD ( n  = 30; age range = 69-80 months) and mainstream children in Pre-primary, Year 1, and Year 2 ( n = 89, age range = 61-96 months) were assessed on a GJT of regular past tense, third person singular, and possessive 's . The GJT was sensitive to developmental differences in mainstream children and differentiated children with DLD from Year 1 and 2 mainstream children, with DLD results consistent with a one-year delay in performance compared to controls. The GJT was the strongest discriminator of membership to a clinically selected sample of children with DLD (ROC curve analysis, area under the curve = 88%). Receptive grammar, receptive vocabulary, and nonword repetition were related to performance on the GJT. The grammaticality judgement of inflectional morphology shows promise as a reliable indicator of DLD and a measure sensitive to developmental differences in mainstream children. GJTs should continue to be explored for clinical application as a potential tool for both assessment and intervention.