On markers of linguistic impairment in autism and their implementation.

Language abilities in autism show considerable variability across linguistic domains: vocabulary, grammar/structural language, and pragmatics (language in context) may be affected to differing degrees and not always simultaneously, as is the case in other neurodevelopmental conditions (NDCs), e.g. Down syndrome, Williams syndrome, or Developmental Language Disorder. This selective review synthesises empirical markers of language impairment across linguistic domains in autism, sometimes in comparison to other NDCs, while also evaluating theoretically driven assessment tools, both established and currently under development, that implement these markers. Core linguistic markers across the autism spectrum include 'social pragmatic' difficulties, i.e. challenges with irony comprehension, referential expression use, and narrative coherence. Impairment in grammar/structural language, such as morphosyntax (e.g., tense marking, passives, relative clauses) and phonology (e.g., consonant clusters, as in str), is observed in a substantial subset of autistic individuals and many other NDCs. Aspects of 'linguistic pragmatics,' such as understanding metaphor and indirect requests, tend to be impaired mainly in autistic individuals who also have structural language difficulties. Other challenges have been reported, including in prosody, semantics and lexical-pragmatics (e.g., mental state terms such as think, fear, happy), but remain underexplored. We further evaluate several existing and emerging screening tools that target specific linguistic markers and accommodate a wide range of populations, including males and females, multilingual speakers, minimally speaking individuals, and those with varying intellectual abilities. Grounded in theoretical linguistics, these tools are designed to facilitate detailed profiling of language strengths and challenges in autism. Their cross-linguistic design and applicability make them well-suited for cross-syndrome comparisons and the development of tailored interventions.