The Locus Preservation Hypothesis: Shared Linguistic Profiles across Developmental Disorders and the Resilient Part of the Human Language Faculty

Abstract

Grammatical markers are not uniformly impaired across speakers of different languages, even when speakers share a diagnosis and the marker in question is grammaticalized in a similar way in these languages. The aim of this work is to demarcate, from a cross-linguistic perspective, the linguistic phenotype of three genetically heterogeneous developmental disorders: specific language impairment, Down syndrome, and autism spectrum disorder. After a systematic review of linguistic profiles targeting mainly English-, Greek-, Catalan-, and Spanish-speaking populations with developmental disorders (n = 880), shared loci of impairment are identified and certain domains of grammar are shown to be more vulnerable than others. The distribution of impaired loci is captured by the Locus Preservation Hypothesis which suggests that specific parts of the language faculty are immune to impairment across developmental disorders. Through the Locus Preservation Hypothesis, a classical chicken and egg question can be addressed: Do poor conceptual resources and memory limitations result in an atypical grammar or does a grammatical breakdown lead to conceptual and memory limitations? Overall, certain morphological markers reveal themselves as highly susceptible to impairment, while syntactic operations are preserved, granting support to the first scenario. The origin of resilient syntax is explained from a phylogenetic perspective in connection to the “syntax-before-phonology” hypothesis.

Diversity of Grammars and Their Diverging Evolutionary and Processing Paths: Evidence From Functional MRI Study of Serbian

“…Recent comparative work that examined linguistic phenotypes across developmental disorders affecting language acquisition converged on the observation that narrow syntax (i.e., the internal computational system) tends to be more resilient than usually thought, i.e., likely to be preserved in many forms of developmental pathology, which by and large affect linguistic phenomena related to externalization, i.e., morphosyntax and morphophonology, linguistic domains that interface with the Intentional-Conceptual and Sensory-Motor systems (The Locus Preservation hypothesis; Leivada et al, 2017 ; Lorenzo and Vares, 2017 ) 10 . We would argue that dissociation in the patterns of language breakdown may reflect distinct underlying brain network organization corresponding to distinct evolutionary stages during which these linguistic domains emerged.…”

Online Processing of Subject–Verb–Object Order in a Diverse Sample of Mandarin‐Exposed Preschool Children with Autism Spectrum Disorder

“…Future cross‐linguistic studies are needed to test to what extent other core grammatical structures, properties, or mechanisms that have been identified in typical language development may also be preserved in language acquisition of children with ASD learning a variety of languages. Such findings may provide evidence that the computational part of the human language faculty may be selectively preserved in at least some children with ASD across languages [Leivada, Kambanaros, & Grohmann, 2017; Su & Su, ].…”

Developing Understandings of Disability through a Constructivist Paradigm: Identifying, Overcoming (and Embedding) Crip-Dissonance

“…However, the behaviour of the disabled person is often not enough to change the non-disabled person's long-term socially constructed and ingrained beliefs about disability. It has been reported that even when there is a discrepancy between preconceived notions and new information, the preconceived notions prevail (Leivada et al 2017).…”