Deductive reasoning in children with specific language impairment.

The diagnosis of specific language impairment (SLI) requires non-verbal ability to be in the normal range, but little is known regarding the extent to which general reasoning skills are preserved during development. A total of 122 children were tested; 40 SLI, 42 age-matched controls, and 40 younger language-matched controls. Deductive reasoning tasks were given in both verbal and pictorial presentation types, namely the relational inference task and the reduced array selection task (RAST). Pictorial presentation facilitated all groups for all tasks equally. For the relational inference task, SLI performance was below both age and language matches. For the RAST, contextual information facilitated all groups equally. SLI performance was intermediate between age and language matches. It is concluded that the non-verbal versus verbal distinction is a complex one and that non-verbal reasoning can draw upon linguistic processes. It is also suggested that SLI reasoning depends upon precise task demands, here the need to sequence information in working memory, and the need for explicit reasoning with conditional rules. Reasoning processes may not be equivalent to normally developing children, even when tasks appear non-verbal.