Processing of verb tense in developmentally language impaired individuals

The present study is an investigation of on-line and off-line processing of verb tense in individuals with developmental language impairment. Three groups of subjects performed two experiments, (1) a lexical decision task (on-line) and, (2) a grammaticality judgement task (off-line). Grammaticality was controlled by the manipulation of tense for regular and irregular verbs. Participants were six members of a large British familial aggregation diagnosed with developmental language impairment, six of their unaffected relatives, and seven unaffected Canadian individuals. The results of the lexical decision task indicate that the reaction times of the affected group were slower than the Canadian control group. Unlike the control groups, the affected group was influenced by regular and irregular verb type distinctions. Reaction times across grammatical and ungrammatical conditions did not differ among the three groups. The groups differed significantly in the off-line task; accuracy of the affected subjects was poor, while the control subjects were highly accurate. The implications of these findings for linguistic theories of SLI such as the missing rules hypothesis (Gopnik, in press) are discussed