Measuring Lexical Diversity in Narrative Discourse of People With Aphasia Purpose A microlinguistic content analysis for assessing lexical semantics in people with aphasia (PWA) is lexical diversity (LD). Sophisticated techniques have been developed to measure LD. However, validity evidence for these methodologies when applied to the discourse of PWA is lacking. The purpose of this study was to evaluate four ... Supplement Article
Supplement Article  |   May 01, 2013
Measuring Lexical Diversity in Narrative Discourse of People With Aphasia
 
Author Affiliations & Notes
  • Gerasimos Fergadiotis
    Arizona State University, Phoenix
  • Heather H. Wright
    Arizona State University, Phoenix
  • Thomas M. West
    Arizona State University, Phoenix
  • Correspondence to Gerasimos Fergadiotis: gfergadiotis@pdx.edu
  • Editor: Swathi Kiran
    Editor: Swathi Kiran×
  • Associate Editor: Jamie Reilly
    Associate Editor: Jamie Reilly×
Article Information
Research Issues, Methods & Evidence-Based Practice / Language Disorders / Aphasia / Supplement: Select Papers From the 42nd Clinical Aphasiology Conference
Supplement Article   |   May 01, 2013
Measuring Lexical Diversity in Narrative Discourse of People With Aphasia
American Journal of Speech-Language Pathology, May 2013, Vol. 22, S397-S408. doi:10.1044/1058-0360(2013/12-0083)
History: Received July 28, 2012 , Revised October 15, 2012 , Accepted January 28, 2013
 
American Journal of Speech-Language Pathology, May 2013, Vol. 22, S397-S408. doi:10.1044/1058-0360(2013/12-0083)
History: Received July 28, 2012; Revised October 15, 2012; Accepted January 28, 2013
Web of Science® Times Cited: 10

Purpose A microlinguistic content analysis for assessing lexical semantics in people with aphasia (PWA) is lexical diversity (LD). Sophisticated techniques have been developed to measure LD. However, validity evidence for these methodologies when applied to the discourse of PWA is lacking. The purpose of this study was to evaluate four measures of LD to determine how effective they were at measuring LD in PWA.

Method Four measures of LD were applied to short discourse samples produced by 101 PWA: (a) the Measure of Textual Lexical Diversity (MTLD; McCarthy, 2005), (b) the Moving-Average Type-Token Ratio (MATTR; Covington, 2007), (c) D (McKee, Malvern, & Richards, 2000), and (d) the Hypergeometric Distribution (HD-D; McCarthy & Jarvis, 2007). LD was estimated using each method, and the scores were subjected to a series of analyses (e.g., curve-fitting, analysis of variance, confirmatory factor analysis).

Results Results from the confirmatory factor analysis suggested that MTLD and MATTR reflect LD and little of anything else. Further, two indices (HD-D and D) were found to be equivalent, suggesting that either one can be used when samples are >50 tokens.

Conclusion MTLD and MATTR yielded the strongest evidence for producing unbiased LD scores, suggesting that they may be the best measures for capturing LD in PWA.

Acknowledgments
This research was partially supported by the National Institute on Aging Grant R01AG029476. Much of the work was completed when the authors were affiliated with Arizona State University in Tempe, AZ. We are especially grateful to the study participants. We also thank the volunteers in the Aging and Adult Language Lab at Arizona State University for assistance with language analyses and Franklin Chen from Carnegie Mellon University for assisting with CLAN coding.
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