Diagnostic criteria of Specific Language Impairment (SLI)

- Language is significantly below level expected from age and IQ, usually interpreted as  scoring in the lowest 10% on a standardized test of expressive and/or receptive language;

- Nonverbal IQ and nonlinguistic aspects of development (self-help skills, social skills) fall within broadly normal limits;

- Language difficulties cannot be accounted for by hearing loss, physical abnormality of the speech apparatus, or environmental deprivation;

- Language difficulties are not caused by brain damage.

Common presenting features*

- Delay in starting to talk; first words may not appear until 2 years of age or later;

- Immature or deviant production of speech sounds, especially in preschool children;

- Use of simplified grammatical structures, such as omission of past tense endings or the auxiliary ‘‘is,’’ well beyond the age when this is usually mastered;

- Restricted vocabulary, in both production and comprehension;

- Weak verbal short-term memory, as evidenced in tasks requiring repetition of words or sentences;

- Difficulties in understanding complex language, especially when the speaker talks rapidly.

* SLI shows substantial heterogeneity, as well as age-related change, and diagnosis does not depend on presence or absence of specific language characteristics.

Source:
Dorothy V.M. Bishop: What Causes Specific Language Impairment in Children? 2006