Specific Language Impairment (SLI)
Specific language impairment is the older diagnostic label, now largely replaced by Developmental Language Disorder but still present in research literature.
What SLI is
Specific Language Impairment (SLI) is the historical diagnostic label for a persistent language deficit that appears in children with otherwise intact nonverbal ability, sensory systems, and social engagement. The CATALISE consensus (Bishop et al. 2017) recommended retiring the term in favour of "Developmental Language Disorder" because the word "specific" implied a degree of domain-specificity that the evidence no longer supports — most affected children have co-occurring attention, working memory, literacy, or motor difficulties. SLI still appears widely in the research literature through about 2018 and in older IEP documents, so clinicians should recognise it as the functional equivalent of DLD for most diagnostic and intervention decisions.
Prevalence
Legacy prevalence figures from Tomblin et al. 1997 put SLI at approximately 7.4% of kindergarten children — essentially identical to current DLD estimates because the diagnostic boundary has moved only marginally.
Diagnostic criteria and defining features
- Language test score at least 1.25 SD below the mean on two or more standardised subtests
- Nonverbal IQ within the normal range (traditionally above 85)
- Normal hearing across speech frequencies
- No medical, neurological, or sensory condition that better explains the language deficit
- Persistent presentation rather than transient delay
Criteria summarised from DSM-5-TR, ICD-11, and ASHA practice guidance. Always cross-reference against the diagnostic manual of record before using in a report.
Clinical presentation
Children historically diagnosed with SLI look identical to children currently diagnosed with DLD — short utterances, tense and agreement errors, reduced lexical diversity, narrative difficulty, and often co-occurring phonological immaturity. The biggest practical difference between the two labels lies not in the presentation but in the eligibility criterion: SLI traditionally required documentation of normal nonverbal IQ (usually a Leiter or TONI score above 85), while DLD has no such cut-off. That distinction matters when reviewing older evaluations — a child labelled "not SLI because IQ too low" under the old criteria may well meet criteria for DLD under the CATALISE framework and should be re-evaluated.
“SLI and DLD are the same children viewed through different consensus panels. If a 2005 report calls a child "SLI" and a 2020 report would call the same child "DLD", the interventions that worked in 2005 are the interventions that will work now.”
How language sample analysis contributes
Research using the SLI label produced much of the published LSA evidence base. Rice et al. 2010, the reference most clinicians cite for MLU norms, studied children labelled with SLI. The extended optional infinitive framework of Rice & Wexler 1996 — finite verb morphology is the signature deficit — came from SLI research and still drives the common clinical observation that past-tense -ed omission is the most diagnostic single error in the early grades. When reading older literature or revisiting an older evaluation, treat SLI-era findings as broadly applicable to modern DLD cases, but note the change in eligibility thresholds.
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Free tools for Specific Language Impairment (SLI)
MLU Calculator
Paste a language sample and get Mean Length of Utterance in morphemes and words, total utterances, total morphemes, and the matching Brown's stage. Implements Brown (1973) morpheme counting rules and runs entirely in your browser.
Open toolDSS Calculator
Free Developmental Sentence Scoring (DSS) calculator for speech-language pathologists. Paste 50 sentences, tap weighted points across the eight Lee (1974) grammatical categories — Indefinite Pronouns, Personal Pronouns, Main Verbs, Secondary Verbs, Negatives, Conjunctions, Interrogative Reversals, Wh-Questions — plus the all-correct sentence point, and the calculator returns the live DSS with a per-category breakdown. Mobile-friendly tap-through grid, client-side, no sign-up.
Open toolIPSyn Calculator
Free Index of Productive Syntax (IPSyn) calculator for speech-language pathologists. Score the 56 Scarborough (1990) grammatical items across the Noun Phrase, Verb Phrase, Question/Negation, and Sentence Structure subscales from a 100-utterance language sample. Live IPSyn total, per-subscale subtotals, sample-size guard, mobile-friendly, client-side, no sign-up.
Open toolRelated disorders
Developmental Language Disorder (DLD)
Developmental language disorder is a persistent language impairment that is not explained by another medical condition and affects roughly 1 in 14 children.
PediatricMixed Receptive-Expressive Language Disorder
A mixed profile describes children whose comprehension and production are both impaired — the most common presentation under the DLD umbrella.
PediatricExpressive Language Delay
Expressive language delay describes children whose spoken output lags behind age expectations while their receptive skills remain within the typical range.
References
- Rice, M. L., & Wexler, K. (1996). Toward tense as a clinical marker of specific language impairment in English-speaking children. JSHR, 39(6), 1239–1257.
- Leonard, L. B. (2014). Children with Specific Language Impairment (2nd ed.). MIT Press.
- Tomblin, J. B., et al. (1997). Prevalence of specific language impairment in kindergarten children. JSLHR, 40(6), 1245–1260.