Acquisition of Turkish grammatical morphology by children with developmental disorders

Many children with specific language impairment, Down syndrome or autism spectrum disorder have difficulty learning grammatical morphology, especially forms associated with the verb phrase. However, except for Hebrew, the evidence thus far has come from Indo-European languages.

This study investigates the acquisition of grammatical morphology by Turkish-speaking children with developmental disorders. Syntactic, perceptual and usage features of this non-Indo-European language were predicted to lead to patterns of atypical learning that would challenge and broaden current views.

Language samples were collected from 30 preschoolers learning Turkish: ten with developmental disorders, ten matched by age and ten by length of utterance. T-SALT then generated mean length of utterance, the total number of noun errors, the total number of verb errors and the per cent use in obligatory contexts for noun suffixes. Analyses also looked at the potential effects of input frequency on order of acquisition.

Turkish children in the MLU-W control group, aged 3;4, used noun and verb suffixes with virtually no errors. Children in the group with atypical language showed more, and more persistent, morphological errors than either age or language peers, especially on noun suffixes. Children in the ALD and MLU-W groups were acquiring noun case suffixes in an order that is strongly related to input frequencies.

These findings seem to reflect the influence of salience, regularity and frequency on language learning. Typical child-adult discourse patterns as well as the canonical SOV Turkish word order make verb suffixes perceptually salient, available in working memory and frequently repeated. The findings support the view that the language patterns seen in children with atypical development will differ from one language type to the next. They also suggest that regardless of language or syntactic class, children will have greater difficulty with those features of grammar that have higher cognitive processing costs.