Approximately 7% of kindergarten children have a primary language disorder characterized by a significant delay in the comprehension or production of spoken language. Although these children have normal intelligence and hearing and are free of obvious neurological deficits such as cerebral palsy and severe emotional disturbances such as autism, their limitations in spoken language often persist throughout childhood, adolescence, and well into adulthood.

In addition, children with this disorder, often called specific language impairment, frequently demonstrate limitations in written language development during the school-age years, including problems in decoding print, comprehending text, spelling, and producing essays for school assignments. Problems in the social use of language, particularly during peer interactions, frequently affect these children as well.