Testing the generalized slowing hypothesis in specific language impairment

This study investigated the proposition that children with specific languag e impairment (SLI) show a generalized slowing of response time (RT) across tasks compared to chronological-age (CA) peers. Three different theoretical models consistent with the hypothesis of generalized slowing-a proportiona l, linear, and nonlinear model-were examined using regression analyses of g roup RT data. Each model was an excellent fit with the RT data. The most pa rsimonious model indicated that the SLI group was proportionally slower tha n the CA group. Mean RTs of the SLI group were about one fifth slower acros s tasks than the CA group's mean RTs. Less slowing was evident for a subgro up of young children with expressive SLI than for children with mixed (expr essive and receptive) SLI. Although the mean RT data reflected many individ ual SLI children's RT performance, not all SLI children showed generalized slowing.