Although learning disability accounts for over one fourth of the handicapped school population, it is the least understood pattern of exceptionality, both with respect to its essential features and developmental consequences. The significance of this research follows from the need to distinguish learning disabled children from other forms of exceptional development and to develop reliable and reproducible criteria for identifying homogeneous LD subgroups which can be attributed to different developmental processes. The purpose of this research is to provide a comprehensive, longitudinal portrait of subtypes of specific learning disabilities, and determine their developmental implications and consequences. Multivariate cluster analysis will be used to divide a heterogeneous sample (n = 200) of LD children and nonspecific underachievers into subtypes based on their pattern of intellectual abilities, academic performance, and adaptive classroom behavior. The selection procedure for this sample is based on the federal definitions for various categories of exceptionality and is carried out independently of school selection and classification procedures. Existing longitudinal data will be used to determine the stability of subtypes over a three-year period, and to trace the development of linguuistic, cognitive and personal/social competences compared to average achievers. Also, analyses are proposed to relate a variety of socioeconomic, family and child preschool variables to subtypes. Finally, we propose to follow-up the longitudinal sample to determine the consequences of sulbtypes of learning disability for school achievement and adjustment at the end of the elementary school period.
