Mixture growth models of RAN and RAS row by row: insight into the reading system at work over time |
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| Authors: | Dagmar Amtmann Robert D Abbott and V W Berninger |
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| Institution: | (1) Department of Rehabilitation Medicine, University of Washington, Box 357920, Seattle, WA 98195-7920, USA;(2) Department of Educational Psychology, University of Washington, 322 Miller Hall, Box 353600, Seattle, WA 98195-3600, USA |
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| Abstract: | Children (n = 122) and adults (n = 200) with dyslexia completed rapid automatic naming (RAN) letters, rapid automatic switching (RAS) letters and numbers,
executive function (inhibition, verbal fluency), and phonological working memory tasks. Typically developing 3rd (n = 117) and 5th (n = 103) graders completed the RAS task. Instead of analyzing RAN/RAS results the usual way (total time), growth mixture modeling
assessed trajectories of successive times for naming 10 symbols in each of five rows. For all three samples and both RAN and
RAS, two latent classes were identified. The “faster” class performed slowly on the first row and increased time by small increments on subsequent rows. The “slower” latent class performed more slowly on the first row, and children, but not adults, increased time by larger increments on subsequent rows. For children, both the initial row (automaticity index) and slope (sustained controlled processing index)
of the trajectory differentiated the classes. For adults, only the initial row separated the classes. The longest time was
on row 3 for RAN and row 4 for RAS. For the typically developing 5th graders, close in age to the children with dyslexia,
the trajectories were flatter than for children with dyslexia and only the slower class (4%) showed the peak on row 4. For
children with dyslexia, inhibition predicted RAN slope within the slower latent class and phonological working memory predicted
RAS slope for both latent classes. For adults with dyslexia, inhibition and phonological working memory differentiated both
latent classes on RAN intercept and RAS slope. Taken together, RAN, which may assess the phonological loop of working memory,
and RAS, which may assess the central executive in working memory, may explain the timing deficit in dyslexia in sustaining
coordinated orthographic-phonological processing over time.
This research was supported by Grant Ns. P50 33812 and R01 HD25858 from the National Institute of Child Health and Human Development,
Virginia W. Berninger, PI. |
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| Keywords: | Rapid automatic naming (RAN) Rapid automatic switching (RAS) Dyslexia Inhibition Phonological working memory Automaticity Controlled processing |
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