Characteristics of Learning Disabilities in Students
To describe the various categories of exceptionality, observers typically list the physical and psychological characteristics often exhibited by the individuals who make up that group. For example, early in the field’s history a task force commissioned to identify the characteristics of children with learning disabilities (the term minimal brain dysfunction was used to describe these children at that time) found that 99 separate characteristics were reported in the literature (Clements, 1966). The inherent danger in such lists is the tendency to assume, or to look for, each of those characteristics in all children considered in the category. This danger is especially troublesome with learning disabilities because the category includes children who exhibit a wide range of learning, social, and emotional problems. In fact, Mercer and Pullen (2005) suggest that it is theoretically possible for an individual with learning disabilities to exhibit one of more than 500,000 combinations of cognitive or socioemotional problems.
Learning disabilities are associated with problems in listening, reasoning, memory, attention, selecting and focusing on relevant stimuli, and the perception and processing of visual and/or auditory information. These perceptual and cognitive processing difficulties are assumed to be the underlying reason why students with learning disabilities experience one or more of the following characteristics: reading problems, deficits in written language, underachievement in math, poor social skills, attention deficits and hyperactivity, and behavioral problems.
Difficulty with reading is by far the most common characteristic of students with learning disabilities. It is estimated that 90% of all children identified as learning disabled are referred for special education services because of reading problems (Kavale & Forness, 2000). Some professionals now believe the term learning disabilities, which encompasses so many different types of learning problems, hinders our understanding of the causes, developmental courses, and outcomes of the reading problems experienced by many children (Fletcher et al., 2002). They recommend developing specific definitions and research bases for each type of learning disability (e.g., reading disabilities, math disabilities).
Evidence suggests that specific reading disability, also called dyslexia, is a persistent deficit, not simply a developmental lag in linguistic or basic reading skills (Lyon, 1995). The International Dyslexia Association defines dyslexia as
a specific learning disability that is neurobiological in origin. It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. (Lyon, Shaywitz, & Shaywitz, 2003, p. 2)
Children who fail to learn to read by the first grade tend to fall farther and farther behind their peers, not only in reading but in general academic achievement as well. For example, longitudinal studies have found that 74% of children who are diagnosed as learning disabled because of reading problems remain disabled in the ninth grade (Fletcher et al., 1994; Stanovich & Siegel, 1994).
Recent research has revealed a great deal about the fundamental nature of children’s reading disabilities and the type of instruction most likely to prevent and remediate reading problems (Jenkins & O’Conner, 2002; Kame’enui, Good, & Harn, 2005; National Reading Panel, 2000; Smith, Baker, & Oudeans, 2001). In summarizing this research, Torgesen and Wagner (1998) state that (1) the “most severe reading problems of children with learning disabilities lie at the word, rather than the text, level of processing” (i.e., inability to accurately and fluently decode single words), and (2) the most common cognitive limitation of these children involves a dysfunction in the awareness of the phonological structure of words in oral language.
Recent research suggests that children with severe reading disabilities, particularly those who are resistant to interventions effective for the majority of struggling readers, may share a second processing problem in addition to deficits in phonological awareness. Many children and adults with dyslexia show a significant deficit in visual naming speed (the ability to rapidly name visually presented stimuli) compared to a typical reader (Lovett, Steinbach, & Frijters, 2000; Wolf, Bowers, & Biddle, 2000). When asked to state the names of visually presented material such as letters, many individuals with reading disabilities have difficulty rapidly retrieving and stating the names of the letters, even though they know the letter names. The term double deficit hypothesis is used to describe children who exhibit underlying deficits in phonological awareness and rapid naming speed (Wolf & Bowers, 2000).
Of course, comprehension is the goal of reading. And comprehension lies at the phrase, sentence, paragraph, and story level, not in identifying single words. But the inability to rapidly identify words impairs comprehension in at least two ways. First, faster readers encounter more words and idea units, thereby having the opportunity to comprehend more. Second, assuming that both word recognition and comprehension consume finite cognitive processing resources, a struggling reader who devotes more processing resources to identify words has “fewer cognitive processing resources . . . available for comprehension. The less efficient word reading of students with reading disabilities overloads working memory and undermines reading comprehension” (Jenkins & O’Conner, 2001, pp. 1–2).
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