Sunday, January 20, 2019

The Role of Nonverbal Working Memory in Morphosyntactic Processing by Children with Specific Language Impairment and Autism Spectrum Disorders

Weismer, S. E., Davidson, M. M., Gangopadhyay, I., Sindberg, H., Roebuck, H. & Kaushanskaya, M. (2017). The role of nonverbal working memory in morphosyntactic processing by children with specific language impairment and autism spectrum disorders. Journal of Neurodevelopmental Disorders, 9(28). doi: 10.1186/s11689-017-9209-6.

The grammar of a language refers to the rules for how we put words and sentences together. One part of grammar is called morphology and refers to the smallest units of meaning in a language. Take, for example, the word ‘jumped’. Jumped has 2 meaningful units or morphemes – the action, jump, and the past tense marker that tells us the action is already over, -ed. Morphemes like ‘-ed’ are called inflectional morphemes, and there are a lot of them in the English language. Like ‘-ed’, some are bound to verbs to signal tense (when something is happening) or agreement (between the subject and verb of a sentence as in he jumps vs. they jump). Others mark nouns as plural (e.g., cups), possessive (e.g., Jill’s), etc. Children with a developmental language disorder (DLD; also known as specific language impairment) have difficulty learning these inflectional morphemes. Some studies also suggest that children with autism spectrum disorder (ASD) have the same kind of trouble with learning morphology.

Both children with DLD and ASD are also reported to have poor working memory. Working memory is a difficulty holding and manipulating information you’re thinking of in the moment. According to one theory, having poor working memory might make it difficult to learn language. If that’s the case, we would expect language tasks to be harder when more language is involved, for example, when sentences are long or complex. If a language error happens early in a sentence when there’s not much to hold in memory, it would be easy to detect the error even if working memory is poor. If a language error happens late in the sentence, however, someone with poor working memory would have a hard time remembering the whole sentence and catching the error. There’s another theory, though, that says that understanding the ends of sentences might be easier. According to the ‘wrap up’ theory, errors occurring later in a sentence will be more easily detected because there is more information or context available later in a sentence to help the child process and notice errors in grammar.

In this study, children who were typically developing or had DLD or ASD completed tests of working memory (for information unrelated to language) and grammar. The grammar test was a “grammatical judgement task” and involved the children listening to a sentence and deciding if that sentence contained any errors in grammar or not. The grammar errors were either close to the beginning or the end of the sentence. The researchers found that the typically developing, DLD and ASD groups did not differ on the test of working memory. On the grammatical judgement task, the researchers found that children with typically developing language skills were better at detecting grammar errors than children with DLD. This result is not surprising considering that children with DLD are known to have difficulty learning the inflectional morphemes that were used as the grammatical errors. As well, all children were better and faster at detecting grammatical errors late in a sentence than those occurring early in a sentence. This finding supports the “wrap-up” account. It suggests that the information in a sentence may help a child to make sense of that sentence and to notice any errors that may exist.

The results of this study suggest that context helps. That is, important details are best provided once a child understands the topic or context being discussed. It might suggest that the strategy of ‘Keep It Short and Simple’ may not be the best strategy for all children. Some children might benefit from having sufficient information to support their understanding.

Blogger: Alyssa Kuiack is a M.Cl.Sc./PhD candidate, in speech-language pathology, working under the supervision of Dr. Lisa Archibald.

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