Defining and classifying learning disabilities and attention-deficit/hyperactivity disorder.

This paper provides an overview of current conceptualizations of learning disabilities and ADHD, a conceptual framework critical for defining and classifying each disorder and for distinguishing each disorder from the other and from other, less common problems of childhood. At a most basic level, reading disability or dyslexia (the most common and best defined of the learning disabilities) and ADHD represent two distinct disorders that may frequently cooccur in the same unfortunate child but that can be clearly distinguished from one another. Reading disability represents a disorder of cognitive functioning. In contrast, ADHD is defined by the child's behavior as perceived by the child's parents and teachers; ADHD thus refers to a disorder affecting primarily the behavioral domain. Within the last decade, considerable progress has been made in our understanding of reading and reading disability. Converging evidence from several lines of investigation now indicates that reading ability conforms to a normal distribution model, so that there is a continuum of reading ability and reading disability. Children along this continuum differ by degree but not in kind. Cutoff points may be instituted to segment this continuous distribution, but these will be arbitrary and will not reflect any natural joints in nature; there is no second mode or "hump" in the distribution of reading ability. The normal model of reading and reading disability indicates that reading disability is related to normal reading ability, that there is a seamless transition from good to poor reading ability. Awareness of this relationship is critical to our approach to understanding the basis of reading disability.(ABSTRACT TRUNCATED AT 250 WORDS)