Logo for the Journal of Rehab R and D

Volume 45 Number 6, 2008
   Pages 901 — 910

Abstract - Models of reading performance in older adults with normal age-related vision

Rolf W. Nygaard, PhD;1 Katharina V. Echt, PhD;1-2 Ronald A. Schuchard, PhD;1,3*

1Atlanta Department of Veterans Affairs Rehabilitation Research and Development Center of Excellence, Atlanta, GA; Departments of 2Medicine and 3Neurology, Emory University School of Medicine, Atlanta, GA

Abstract — Reading rate with print size (reading performance) was studied in a group of 132 older readers with normal age-related vision using the Minnesota Low Vision Reading Acuity (MNREAD) test. Regression by a monotonic Weibull model had greater convergence success with lower residual error than either Logistic or Gompertz models. Reading performance by Weibull model regression was characterized by inflexion slope, critical print size, and maximum reading rate. Successive shortening of the data set length before regression by the monotonic Weibull model gave decreased fitting error. This finding suggests that some individual reading rates, rather than asymptoting at the largest print size, may give nonsigmoidal responses. Shortening the data set length decreases regression error but significantly changes regression parameter values. A nonmonotonic Weibull model that was sensitive to declining reading rate at large print size improved regression on 22% of our data. This result indicates that a subgroup of subjects had response falloff at large print size and reading performance characteristics that included incremental and decremental reading rate slopes at different print sizes, which were separated by a reading rate plateau.

Key words: Gompertz model, growth models, Logistic model, MNREAD, nonlinear regression, normal readers, reading, reading rate, rehabilitation, sigmoidal models, Weibull model.

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