The authors point out that much of learning disabilities research relies on categorical classification frameworks that use psychometric tests and cut points to identify children with reading or math difficulties, and there is increasing evidence that the attributes of reading and math learning disabilities are dimensional, representing correlated continua of severity. The authors discuss issues related to categorical and dimensional approaches to reading and math disabilities, and their comorbid associations, highlighting problems with the use of cut points and correlated assessments.
Branum-Martin, Lee, Fletcher, Jack M., and Stuebing, Karla K. (2013). Classification and Identification of Reading and Math Disabilities – The Special Case of Comorbidity. Journal of Learning Disabilities, 46, 490-499.