Many of the language deficits exhibited by children with specific language impairment (SLI) can be described as “verb-related”. The purpose of the current study was to investigate the lexical properties of verbs in the language of children with and without SLI. Three planned experiments targeted this issue with different experimental tasks. The participants were 16 children with SLI (ages 8;5-12;6), and 16 age-matched typically language developing (TLD) children. A group of 16 adults (ages 18-21) have also participated in Experiment 3.

In Experiment 1, the production of sentences for specific verbs, in relation to the number and type of arguments and complements, was analyzed. Children with SLI were found to produce more errors and they responded with more “ don't know” (DK) responses, as compared with their TLD peers.

In Experiment 2, a grammaticality judgment task assessed the children's sensitivity to specific types of sentential complements that certain verbs select. Children with SLI were found to produce more judgment errors and to produce more errors when they attempted to correct ungrammatical sentences, as compared with their TLD peers.

In Experiment 3, verb activation during on-line sentence comprehension was targeted. The goal was to determine which structural characteristics of verbs affect the time it takes children with SLI, children with TLD, and adult listeners, to activate verbs from the mental lexicon. Three variables were examined: (a) the number of arguments, (b) the number of structural options, and (c) the thematic structure. An online pitch change method was employed. Analysis of reaction times revealed that the number of structural options was the crucial factor that affected verb processing. It created complexity effects for all three groups of participants. Children with SLI were affected by the lexical characteristics of verbs in the same way as the two control groups.

These results show a dissociation between the normally appearing verb activation mechanism of children with SLI, and their difficulty in translating this implicit knowledge into explicit linguistic knowledge required for performing a variety of production and comprehension tasks. An individual perspective showed, however, that not all children with SLI were impaired on the non-online measures.