Same IQ, Different Language: Russian Study Reveals Distinct Linguistic Profiles in Autism vs. Down Syndrome

The standard clinical assumption: language delay in neurodevelopmental disorders is driven primarily by cognitive ability. Lower IQ → worse language. This collaborative study from HSE University's Center for Language and Brain and МГППУ's Federal Resource Center for ASD challenges that assumption directly. When you match children with ASD and Down syndrome on non-verbal IQ, their language profiles are not the same — and the differences point to fundamentally different linguistic processing mechanisms.

The phonology split

This is the study's sharpest finding. Children with ASD outperformed children with Down syndrome on phonological processing tasks — sound-level language operations. This maps onto the known profiles: Down syndrome involves motor speech difficulties and phonological memory deficits that constrain sound processing. ASD typically preserves phonological processing while impairing pragmatic and social language use.

The implication for speech-language therapy: the same "language-delayed child" label produces different therapy targets depending on the diagnosis. A child with Down syndrome needs phonological intervention. A child with ASD may need less phonological work but more work on flexible word retrieval and non-canonical sentence structures.

The verb-noun and word-order asymmetries

The ASD group showed two additional specific patterns. First, they struggled more with verbs than nouns in naming tasks — consistent with the broader finding that verb processing requires more syntactic and event-structure knowledge, which is selectively impaired in ASD. Second, they comprehended canonical SVO sentences ("The cat chased the dog") better than non-canonical OVS sentences ("The dog was chased by the cat") — suggesting difficulty with flexible syntactic reanalysis.

These are not global language deficits. They are structural, predictable, and targetable.

For your practice

For clinicians assessing bilingual Russian-speaking children or working with Russian language assessment tools: the Russian Child Language Assessment Battery is validated across phonology, lexicon, and morphosyntax. For speech-language pathologists: match your intervention target to the diagnosis, not the IQ score. ASD → focus on verbs, non-canonical structures, pragmatic flexibility. Down syndrome → focus on phonological processing and motor speech. For researchers: this study demonstrates that IQ-matching reveals diagnosis-specific linguistic mechanisms — a methodological lesson applicable beyond Russian.