Age-dependent semantic interference effect on propositional speech production.

Older adults can find verbal communication in noisy environments challenging, but the underlying cognitive phenomena and the specific mechanisms contributing to age-related decline remain unclear. Using a newly designed propositional speech production paradigm, we examined how semantic distractors of varying levels of relatedness affect propositional speech performance in healthy adults. In the paradigm, participants were assessed on their ability to formulate verbal responses while distracted by semantically related or unrelated words, simulating real-world scenarios with meaningful auditory distractions (e.g., sounds from radio programs). We also examined the cognitive processes associated with task performance. We recruited 30 younger participants (mean age: 22.23 years) and 27 older participants (mean age: 75.31 years) matched for sex, handedness, and intelligence. All participants were screened using the Montreal Cognitive Assessment (MoCA) and neuropsychological assessments. Older adults performed better than younger adults on a semantic memory task, but performed poorer on tasks assessing executive functions, including interference control, verbal response initiation and suppression, and semantic verbal fluency. In the novel propositional speech production task, older adults exhibited a pronounced semantic interference effect (F = 4.67, p = .018, ηp = .08; with MoCA as a covariate), particularly for concrete distractors, resulting in longer response latencies compared to associative and unrelated distractors (Bonferroni-corrected P-values <.01). Exploratory correlation analyses revealed that longer response latencies in the propositional speech production task were associated with a poorer performance on neuropsychological tests tapping verbal response suppression (false discovery rate-corrected p < .05). Our findings suggest that verbal communication difficulties in the context of environmental distractions experienced by older adults could be due to the semantic interference effect. Cognitive interventions aimed at enhancing inhibitory control could be beneficial to older adults in maintaining their social engagement in the later life.