General Slowing in Language Impairment Methodological Considerations in Testing the Hypothesis Research Article
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Research Article  |   April 01, 2001
General Slowing in Language Impairment
 
Author Affiliations & Notes
  • Jennifer Windsor
    University of Minnesota Minneapolis
  • Rochelle L. Milbrath
    University of Minnesota Minneapolis
  • Edward J. Carney
    University of Minnesota Minneapolis
  • Susan E. Rakowski
    University of Minnesota Minneapolis
  • Corresponding author: e-mail: windsor@umn.edu
  • Currently affiliated with Addison North Supervisory Union, Vergennes, VT
    Currently affiliated with Addison North Supervisory Union, Vergennes, VT×
Article Information
Research Issues, Methods & Evidence-Based Practice / Language Disorders / Language / Research Articles
Research Article   |   April 01, 2001
General Slowing in Language Impairment
Journal of Speech, Language, and Hearing Research, April 2001, Vol. 44, 446-461. doi:10.1044/1092-4388(2001/036)
History: Received June 2, 2000 , Accepted January 3, 2001
 
Journal of Speech, Language, and Hearing Research, April 2001, Vol. 44, 446-461. doi:10.1044/1092-4388(2001/036)
History: Received June 2, 2000; Accepted January 3, 2001
Web of Science® Times Cited: 41

Although the general slowing hypothesis of language impairment (LI) is well established, the conventional method to test the hypothesis is controversial. This paper compares the usual method, ordinary least squares regression (OLS), with another method, hierarchical linear modeling with random coefficients (HLM). The analyses used available response time (RT) data from studies of perceptual-motor, cognitive, and language skills of LI and chronological-age-matched (CA) groups. The data set included RT measures from 25 studies investigating 20 different tasks (e.g., auditory detection, mental rotation, and word recognition tasks). OLS and HLM analyses of the RT data yielded very different results. OLS supported general slowing for the LI groups, and indicated that they were significantly slower than CA groups across studies by an overall estimate of 10%. HLM indicated a larger average extent of LI slowing (18%). However, the variability around this average was much greater than that yielded by OLS, and the extent of slowing was not statistically significant. Importantly, HLM showed a significant difference in the RT relation between LI and CA groups across studies, indicating that study-specific slowing, rather than general slowing across studies, was present. A separate HLM analysis of two types of language tasks, picture naming and word recognition, was performed. Although the extent of slowing was equivalent across these tasks, the slowing was minimal (2%) and not significant. Methodological limitations of each analysis to assess general slowing are highlighted.

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