James Law, Ph.D., FRCSLT, Professor of Language and Communication Science, Director of the Centre for Integrated Healthcare Research, Queen Margaret University 
Published online 02-13-09 in the Canadian Language & Literacy Research Network in their Encyclopedia of Language and Literacy Development
This Encyclopedia entry summarises what we know about outcomes for children with Primary Language Impairment (PLI)1, and considers the potential role of intervention in modifying outcomes. The term “primary language impairment” is employed here rather than Specific Language Impairment (SLI) (Plante, 1998; Stark & Tallal, 1981) to obviate the need for the use of a strict discrepancy definition of SLI. SLI requires tested “normal” non-verbal IQ with a one standard deviation discrepancy between verbal and non-verbal skills, PLI does not. However, the term PLI does retain a distinction between those children whose difficulties are mainly associated with their communication and those for whom their communication difficulties are secondary to other conditions (e.g., autism, cerebral palsy, etc.).
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