Age-Related Differences in Production of Non-Canonical Syntactic Structures as a Function of Modifiers to Noun Phrases

Objectives: This current study investigated age-related differences in production of non-canonical syntactic structures when the function of modifiers to noun phrases (NPs) was systematically manipulated. We manipulated the modifiers by varying the length and location of modifiers in relation to the NPs. Methods: A total of 100 individuals (young 50s, elderly 50s) participated in the study. We developed a sentence rearrangement task, in which the sentential segments were randomly presented in a computer screen and participants were asked to construct a sentence by rearranging the segments (Subject, Object, Verb). The syntactic structures which were presented to participants consisted of three conditions: 1) No modifier, 2) Modifiers with a Long-Subject, and 3) Modifiers with a Long-Object. Results: The elderly group demonstrated significantly lower accuracy across all conditions compared to the younger group. Both groups presented lower performance under the condition of modifiers either with a long object or with a long subject compared to the condition without modifiers. Elderly adults demonstrated differentially greater difficulties in constructing sentences with modifiers with a long object than the other conditions. Results from the ratio of non-canonical syntactic structures revealed that the elderly group showed a higher ratio of non-canonical sentences under the long-object condition. The significant predictors for the ratio of non-canonical syntactic structures in the elderly group were the working memory and the delayed recall test score that accounted for approximately 30.4%. Conclusion: The elderly group demonstrated greater difficulties in sentence construction tasks. When the cognitive load increased through manipulating of the location and length of modifiers to the NPs, elderly adults exhibited a higher ratio of producing non-canonical structures, indicating that they employed a strategy to engage the non-canonical structures to reduce the cognitive burden from the long-object modifiers.