GRAMMATICAL ERRORS IN SPECIFIC LANGUAGE IMPAIRMENT - COMPETENCE OR PERFORMANCE LIMITATIONS

Speech samples from twelve 8- to 12-year-old children with specific la nguage impairment (SLI) were analyzed. The feature deficit hypothesis maintains that SLI children may produce morphological markers (e.g., p lural -s) correctly, but they do not appreciate their role in marking grammatical features. Rather, they treat them as meaningless phonologi cal variants. Findings from the present study were incompatible with t his hypothesis: (a) production of morphological markers was not random ; errors were unidirectional, in almost all cases involving omission o f an inflection in an obligatory context; (b) overregularization error s were sometimes observed; (c) grammatical features differed in diffic ulty; (d) substitution of stems for inflected forms occurred with irre gular as well as regular verbs; and (e) errors of pronoun case marking were common and always involved producing an accusative form in a con text demanding the nominative. Children who used a specific inflection al form correctly in some utterances omitted it in others, suggesting a limitation of performance rather than competence. There were few obv ious differences between utterances that did and did not include corre ctly inflected forms, though there was a trend for grammatical errors to occur on words that occurred later in an utterance. It is suggested that slowed processing in a limited capacity system that is handling several operations in parallel may lead to the omission of grammatical morphemes.