Journal Issue: Special Education for Students with Disabilities Volume 6 Number 1 Spring 1996
Approximately one-half of all children receiving special education services nationally, or about 5% of the total public school population, are identified as having a learning disability (LD) when the federal definition of LD is used by schools to formulate identification criteria.1 At the same time, LD remains one of the least understood and most debated disabling conditions that affect children. Indeed, the field continues to be beset by pervasive, and occasionally contentious, disagreements about the definition of the disorder, diagnostic criteria, assessment practices, treatment procedures, and educational policies.2-6
Learning disability is not a single disorder, but is a general category of special education composed of disabilities in any of seven specific areas: (1) receptive language (listening), (2) expressive language (speaking), (3) basic reading skills, (4) reading comprehension, (5) written expression, (6) mathematics calculation, and (7) mathematical reasoning. These separate types of learning disabilities frequently co-occur with one another and also with certain social skill deficits and emotional or behavioral disorders such as attention deficit disorder. LD is not synonymous with reading disability or dyslexia although it is frequently misinterpreted as such.7,8 However, most of the available information concerning learning disabilities relates to reading disabilities, and the majority of children with LD have their primary deficits in reading.2
Box 1 shows the statutory definition of learning disabilities contained in the Individuals with Disabilities Education Act (IDEA). An important part of the definition of learning disabilities under the IDEA is the exclusionary language: learning disabilities cannot be attributed primarily to mental retardation, emotional disturbance, cultural difference, or environmental or economic disadvantage. Thus, the concept of learning disabilities embedded in federal law focuses on the notion of a discrepancy between a child's academic achievement and his or her apparent capacity and opportunity to learn. More succinctly, Zigmond notes that "learning disabilities reflect unexpected learning problems in a seemingly capable child."9
Although poverty and disability are often found together and each tends to exacerbate the other (see the article by Wagner and Blackorby in this journal issue), Congress has established separate programs to serve children with disabilities (the IDEA) and children in poverty (Title 1). Title 1 of the Elementary and Secondary Education Act provides funding for supplemental programs in schools serving large numbers of economically disadvantaged children. Because individual children with disabilities have strong entitlements to services under the IDEA, Congress's intent was that the IDEA serve only children with "true disabilities" and that the IDEA specifically exclude those students whose underperformance is primarily attributable to poverty. However, in the category of learning disability, and perhaps also in the category of mental retardation, this distinction is difficult or impossible to draw, and no empirical data exist to support this exclusionary practice.
While there is some agreement about these general concepts, there is continued disagreement in the field about diagnostic criteria, assessment practices, treatment procedures, and educational policies for learning disabilities. A number of influences have contributed to these disagreements which, in turn, have made it difficult to build a generalizable body of scientific and clinical knowledge about learning disabilities and to establish reliable and valid diagnostic criteria.4,5 While some progress has been made during the past decade in establishing more precise definitions and a theoretically based classification system for LD,8-10 it is useful to understand these historical influences because of their continuing impact on diagnostic and treatment practices for children with learning disabilities.
The next section of this article reviews briefly the historical events that have molded the field of learning disabilities into its present form. Subsequent sections address issues related to the prevalence of learning disabilities, the validity of current prevalence estimates, impediments to the identification and teaching of the child with LD, advances in identification, classification, intervention practices in the area of reading disability, comorbidity of types of learning disabilities (reading, written expression, mathematics disabilities) with disorders of attention and social skills deficits, outcomes for individuals with learning disabilities, and the implications for teacher preparation and school policies.