Effects of syntactic complexity on a case marker processing task in people with mild cognitive impairment

Objectives: Korean syntactic structure is characterized by having case makers as an index of grammatical function. The purpose of the current study was to investigate whether people with mild cognitive impairment (MCI) performed differently from normal elderly adults (NEA) in a case marker processing (CMP) task. Methods: Sixteen individuals with MCI and 20 NEA matched for age and education participated in the study. In the CMP task, nouns and verbs were provided and participants were required to select a case marker. A picture was displayed on a computer monitor and participants were asked to touch the computer screen by selecting a relevant case marker between the three case markers. The CMP task consisted of five different syntactic structures: 1) coordinate conjunction, 2) subject- subject relative clause, 3) subject-object relative clause, 4) object-object relative clause, and 5) object-subject relative clause. Accuracy on the CMP task was analyzed using a twoway mixed ANOVA. Results: The results revealed that the MCI group performed significantly worse than the NEA group. In the case of sentence type, the case makers with a canonical order generated higher accuracy than those with a non-canonical order. There was no significant interaction effect between the sentence type and the group. Conclusion: The results were inconsistent with previous findings that the syntactic abilities were preserved in the MCI group in spontaneous speech tasks. Because of the syntactic complexity of the Korean language, it is required to consider the order and canonicity of case marker assignment as one of the critical contributors of the complexity.