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.

Reading 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).

Written Language Deficits

Many students with learning disabilities have problems with writing and spelling. When compared to their peers without disabilities, students with learning disabilities perform significantly lower across most written expression tasks, especially vocabulary, grammar, punctuation, and spelling (Newcomer & Barenbaum, 1991). Some students have a specific disability with written language.

Compounding the weak language base that many students with learning disabilities bring to the writing task is an approach to the writing process that involves minimal planning, effort, and metacognitive control (Englert et al., 1991; Graham & Harris, 1993). Many of these students use a “retrieve-and-write” approach in which they retrieve from immediate memory “whatever seems appropriate and write it down” (De La Paz & Graham, 1997, p. 295). They seldom use the self-regulation and self-assessment strategies of competent writers: setting a goal or plan to guide their writing, organizing their ideas, drafting, self-assessing, and rewriting. As a result, they produce poorly organized compositions containing a few poorly developed ideas (Sexton, Harris, & Graham, 1998).

Fortunately, the writing and spelling skills of most students with learning disabilities can be improved through strategy instruction, frequent opportunities to practice writing, and systematic feedback (Alber & Walshe, 2004; Goddard & Heron, 1998; Graham & Harris, 2003; Marchisan & Alber, 2001; Scott & Vitale, 2003; Williams, 2002).

Math Underachievement

Numerical reasoning and calculation pose major problems for many students with learning disabilities. Students with learning disabilities perform lower than normally achieving children with every type of arithmetic problem at every grade level (Cawley, Parmar, Foley, Salmon, & Roy, 2001). Deficits in retrieving number facts and solving story problems are particularly evident (Jordan & Hanich, 2000; Ostad, 1998). The math competence of students with learning disabilities progresses about 1 year for every 2 years in school, and the skills of many children plateau by age 10 or 12 (Cawley, Parmar, Yan, & Miller, 1998).

Given these difficulties, it is not surprising that more than 50% of students with learning disabilities have IEP goals in math (Kavale & Reese, 1992). As with reading and writing, explicit, systematic instruction that provides guided, meaningful practice with feedback usually improves the math performance of students with learning disabilities (e.g., Fuchs & Fuchs, 2003; Gagnon & Maccini, 2001; Owen & Fuchs, 2002; Marsh & Cooke, 1996; Witzel, Mercer, & Miller, 2003).

Social Skills Deficits

After reviewing 152 different studies, Kavale and Forness (1996) concluded that about 75% of students with learning disabilities exhibit deficits in social skills. Poor social skills often lead to rejection, low social status, fewer positive interactions with teachers, difficulty making friends, and loneliness—all of which are experienced by many students with learning disabilities regardless of classroom placement (Haager & Vaughn, 1995; Ochoa & Palmer, 1995; Pavri & Monda-Amaya, 2000). The poor social skills of students with learning disabilities may be due to inability to perceive emotions of others, specifically nonverbal affective expressions (Most & Greenbank, 2000).

Some students with learning disabilities, however, experience no problems getting along with their peers and teachers. For example, Sabornie and Kauffman (1986) reported no significant difference in the sociometric standing of 46 learning disabled high school students and 46 peers without disabilities. Moreover, they discovered that some of the students with learning disabilities enjoyed socially rewarding experiences in inclusive classrooms.

One interpretation of these contradictory findings is that social competence and peer acceptance are not characteristics of learning disabilities but outcomes of the different social climates created by teachers, peers, parents, and others with whom students with learning disabilities interact (Vaughn, McIntosh, Schumm, Haager, & Callwood, 1993). Researchers have begun to identify the types of problems experienced by children with learning disabilities who are ranked low in social acceptance and to discover instructional arrangements that promote the social status of students with learning disabilities in the regular classroom (Bryan, 1997; Court & Givon, 2003; Vaughn, Elbaum, & Schumm, 1996).

Attention Problems and Hyperactivity

Some students with learning disabilities have difficulty attending to a task and/or display high rates of purposeless movement (hyperactivity). Children who consistently exhibit this combination of behavioral traits may be diagnosed as having attention-deficit/hyperactivity disorder (ADHD).

Behavioral Problems

Some students with learning disabilities display behavioral problems in the classroom. Research has consistently found a higher-than-normal rate of behavioral problems among students with learning disabilities (Cullinan, 2002). In a study of 790 students enrolled in K–12 learning disabilities programs in Indiana, the percentage of students with behavioral problems (15%) remained consistent across grade levels (McLeskey, 1992). Although these data definitely show increased behavioral problems among children with learning disabilities, the relationships between the students’ behavior problems and academic difficulties are not known. In other words, we do not know whether the academic deficits or the behavioral problems cause the other difficulty. And it is important to note that many children with learning disabilities exhibit no behavioral problems at all.

Regardless of the interrelationships of these characteristics, teachers and other caregivers responsible for planning educational programs for students with learning disabilities need skills in dealing with social and behavioral difficulties as well as academic deficits.

The Defining Characteristic

Although students who receive special education under the learning disabilities category are an extremely heterogeneous group, it is important to remember that the fundamental, defining characteristic of students with learning disabilities is specific and significant achievement deficits in the presence of adequate overall intelligence.

The difference between what students with learning disabilities “are expected to do and what they can do . . . grows larger and larger” over time (Deshler, Schumaker, & Lenz, 2001, p. 97). The performance gap becomes especially noticeable and handicapping in the middle and secondary grades, when the academic growth of many students with disabilities plateaus. By the time they reach high school, students with learning disabilities are the lowest of the low achievers, performing below the 10th percentile in reading, written language, and math (Hock, Schumaker, & Deshler, 1999).

The difficulties experienced by children with learning disabilities—especially for those who cannot read at grade level—are substantial and pervasive and usually last across the life span (Price, Field, & Patton, 2003). The tendency to think of learning disabilities as a “mild” disability erroneously supports “the notion that a learning disability is little more than a minor inconvenience rather than the serious, life-long condition it often is [and] detracts from the real needs of these students” (Hallahan, 1998, p. 4).