The Competition–Compensation Account of Developmental Language Disorder
Published in CSS proceedings, 2021
Harmon, Z., Barak, L., Shafto, P., Edwards, J., & Feldman, N. (2021). Making Heads or Tails of it: A Competition–Compensation Account of Morphological Deficits in Language Impairment. Proceedings of the Annual Conference of the Cognitive Science Society, 43, 1872–1878. [Paper]
Children with developmental language disorder (DLD) regularly use the base form of verbs (e.g., dance) instead of inflected forms (e.g., danced). We propose an account of this behavior in which processing difficulties of children with DLD disproportionally affect processing novel inflected verbs in their input. This leads the inflected form to face stronger competition from alternatives, reducing its productivity. Competition is resolved through a compensatory behavior which involves producing a more accessible alternative with high phonological and semantic overlap with the inflected form: in English, the bare form. Using a nonparametric Bayesian model, we show that the reduction in the number of novel inflected forms in the input of the DLD model leads to additional opportunities for processing verbs as unanalyzed chunks and fewer opportunities to parse the inflected from independently of co-occurring stems. We further show that such a bias in a model with impaired processing could exaggerate difficulties with productive use of inflectional suffixes. Together, the results suggest that inconsistent use of inflectional morphemes by children with DLD could stem from a combination of processing difficulties that affect novelty detection combined with a resulting learned bias to rely on unanalyzed chunks during processing.