Objective and subjective clustering (Fisher et al., 2023)

Purpose: The verb fluency task has been researched using a variety of analysis methods and shown its sensitivity to declines in executive functioning and lexical retrieval abilities in various neurogenic populations. Few studies to date, however, have analyzed clusters and switches in the task, and there is a lack of robust analysis methods that preclude subjectivity and potential rater bias. The purpose of this study was to investigate the reliability when using subjective clustering methods and to determine the feasibility of using an objective clustering method to determine verb fluency performance in individuals with Alzheimer’s dementia (IwDs) and cognitively healthy older adults (CHOAs).

Method: Responses from a verb fluency task were obtained from IwDs and CHOAs. Group differences were examined using an objective clustering method for multiple variables regarding clustering and switching. We also calculated the intrarater, interrater, and intermethod reliability using intraclass coefficients.

Results: Significant group differences were found when utilizing the objective clustering method in all variables except the average cluster size, with IwDs performing poorer than CHOAs. Intrarater reliability was excellent. Interrater reliability between two authors and intermethod reliability between the objective and subjective methods were variable ranging from moderate to good.

Conclusions: The results from using the objective clustering method in this study are consistent with the previous literature, making it a viable option for clustering analyses on the verb fluency task, which naturally minimizes subjectivity and rater bias. Alternatively, employing a thoroughly validated and reliable subjective approach can also mitigate potential rater bias and improve replicability across studies.

Supplemental Material S1. Correlations between all variables across all participants.

Supplemental Material S2. Correlations between all variables in cognitively healthy older adults.

Supplemental Material S3. Correlations between all variables in participants with Alzheimer’s Disease.

Supplemental Material S4. Detailed data.

Fisher, M. N., Casenhiser, D. M., & Paek, E. J. (2023). Objective and subjective clustering methods for verb fluency responses from individuals with Alzheimer’s dementia and cognitively healthy older adults. American Journal of Speech-Language Pathology, 32(5S), 2589–2601. https://doi.org/10.1044/2023_AJSLP-22-00290

Publisher Note: This article is part of the Special Issue: Select Papers From the 51st Clinical Aphasiology Conference.