Morphological richness account as a theory (non)explaining language performance of preschool children with language impairment
Abstract
The paper focuses on how the acquisition of morphology differs in preschool children with language impairment (LI) and children with typical language development (TD). Language impairment is a disorder that primarily affects the linguistic area, but mild deficits in various cognitive functions may also occur.
Theory that addresses how the limitation of cognitive function is reflected in language acquisition is the morphological richness account (Leonard, 2014; MRA). Both the limitation of the capacity of the mind to process information and the language that children learn affect the acquisition of language.
Child uses its capacity of the mind primarily in the acquisition of those grammatical features that are more important in the grammar of the given language (their acquisition in children with LI should be delayed, but it should not be a selective problem for children). However, children with LI should have worse performance than TD children when inflections express more than 3 grammatical categories, as they require higher processing costs and children need more time to their acquisition.
However, children should have some knowledge of these inflections even before their full acquisition, therefore they should use "near-miss errors", which resemble to the target form. If this is not the case, a more frequent inflection should be used.
This work compares the acquisition of verbs and nouns by children with LI and two years younger children with TD who had the same results in the vocabulary test. The sentence repetition with masked suffixes was used (the sentence repetition is a good indicator of language impairment, even when the working memory is controlled; Smolík, Vávrů, 2014).
The research was inspired by studies in Hungarian (Lukács et al., 2009; Lukács et al., 2010). Czech is a flective language, therefore it was assumed (according to the MRA) that children should invest their capacity of mind in learning morphology, and thus have the same results with younger children in declension, except verb inflections, because verb suffixes mostly express 4 and more morphological categories, so they should be more difficult than nouns.
In this work this was not confirmed - the verbs turned out to be easier for children with LI and there was no significant difference in using inflections between the two groups of children. The near-miss errors prevailed, but if they were not used, substitutions were not always more frequent.
Overall, therefore, the MRA assumptions in this research were only partially confirmed. However, both the task and the linguistic characteristics of Czech could play a role in the results.