Specific language impairment (SLI) is a developmental language disorder that can affect both expressive and receptive language. SLI is a "pure" language impairment, meaning that is not related to or caused by other developmental disorders. Children with SLI may acquire language in the same sequence as normally-developing children, but at a slower rate. SLI manifests itself in different ways across individuals, but a hallmark of SLI is difficulty with inflected forms of words. For instance, a native speaker of English who had SLI might not always use "-ed" to mark regular past tense forms of verbs.

SLI affects around 6% of the population, of which a quarter are severely impaired. Boys are more affected than girls, and it usually affects both members of monozygotic twins.

In order to classify a disorder as specific language impairment, it is often considered necessary for the verbal IQ to be at least 20 points below the non-verbal IQ. This can cause problems in the diagnosis of SLI when for example studying twins of approximately equal non-verbal intelligence if the verbal intelligence is not substantially worse.

In some cases, SLI may be inherited. It appears to be related to the FOXP2 gene.

See also

• Grammatical specific language impairment

Notes

1. Gopnik, M. and Goad, H. (1997) "What underlies inflectional error patterns in genetic dysphasia?" in Journal of Neurolinguistics Vol. 10, No. 2-3. pp. 109-137

References

• Hoff, Erika (2005). Language Development (3rd ed.). Belmont: Wadsworth. ISBN 0-534-64170-9.
• Shipley, Kenneth G. & McAfee, Julie G. (2004). Assessment in Speech-Language Pathology: A Resource Manual (3rd ed.). Clifton Park: Thomson. ISBN 1-4018-2751-9.