A number of researchers have suggested taking a multidimensional approach to defming reading disabilities (e.g., Johnson, 1 988; McKinney, 1 988; Senf, 1 986; Tindal & Marston, 1 986). In a similar vein, Keogh (1 987) suggested that rather than trying to constrain the various characteristics of LD or RD children into a single, all-encompassing definition, it would .be preferable to acknowledge that these different characteristics depict different types of learning disabilities. Keogh's (1 987) approach reflects the view of other writers (e.g., McKinney, 1988) who see merit in identifying reading disability subtypes. For instance, a number of investigators have made efforts to categorize these children into more homogeneous subgroups based on neuropsychological processing measures (Petrauskas & Rourke, 1 979), reading and spelling abilities (Boder, 1 973), and visual-spatial and linguistic measures (Spreen & Haaf, 1 986). Unfortunately, the subtyping literature is often confusing and contradictory, resulting in disagreement amongst theorists on the taxonomy of subtypes (Kamhi & Catts, 1 989). For a more thorough discussion of reading subtypes, the reader is referred to a number of excellent reviews and books (Hooper & Willis, 1 989; Kavale & Fomess, 1987; Keogh, 1 988a; McKinney, 1 988; Senf, 1 986; Torgesen, 1982a).
Identifying LD or RD children in terms of their "intraindividual" differences (Chalfant, 1 989; Kirk & Chalfant, 1 984) represents another form of the multidimensional approach used by some researchers (e.g., Evans, 1992). In this approach, LD children are characterized by discrepancies between intelligence and achievement, by differences between psychological processes or developmental abilities, and by differences between performance on different tasks or between academic areas. Thus, the mentally retarded child or slow learner is likely to show fairly consistent, low levels of achievement. In contrast, the LD child would show an inconsistent profile as he or she usually achieves well or adequately in some areas, but poorly in others. This concept of an inconsistent ability profile has been emphasized by Keogh (1 988b ), as a marker for learning disabilities as opposed to the ability-achievement discrepancy that characterizes both mental retardation and learning disabilities.
There is also growing advocacy for viewing decision making concerning definition as a multistage rather than a single stage process. Increasingly, multistage or multidefmitional assessments are advocated as one way of improving the diagnosis of reading disabilities, thus reducing the number of false-positive fmdings (Berninger et al., 1 992; Kavale, Fomess, & Lorsbach, 1 99 1 ; Leong, 1 985, 1987). For instance, Kavale et al. ( 1 99 1 ) suggested that a
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suitable operational definition for a multivariate phenomenon like learning disability can be obtained by extending the view that a definition can include a number of elements or concepts (that may be defined operationally) rather than a single element. The elements chosen, known as "operational interpretations", could be based on validated components representing the areas which have sufficient theoretical importance to the learning disability concept. K.avale et al. illustrated how operational interpretations may be combined to form a comprehensive operational definition for classifying learning disabilities. They proposed a five level hierarchical sequenced operational definition of learning disabilities based on a number of operational interpretations extracted from what is known about the learning disability phenomenon. In their model, discrepancy was represented in the first level followed by four additional levels. The presence of academic problems and poor learning efficiency were represented in levels 2 and 3, followed by the presence of specific skill deficits on the last two levels.
In a similar vem, Leong ( 1 985, 1 987) proposed a two-stage framework of diagnosis incorporating standardized achievement tests and teachers' estimates of children's performance at the assessment stage, and more refmed, individual
tasks
at the diagnostic stage. Empirical support is provided by Berninger et al. (I 992) for a two-stage approach analogous to the framework of Leong ( 1 985, 1 987). In stage 1 classroom teachers were asked to identify "low functioning" children in a variety of beginning reading skills (e.g., orthographic and phonological coding, and perceptual motor integration skills). Stage 2 concentrated on a more comprehensive psychoeducational assessment for children whose problems persisted.The abovementioned multifaceted approaches appear to be a promising avenue for defining
RD children. However, to date little progress has been made in employing such approaches, particularly with regard to the multidefmitional approach. The significance of these approaches lies in their attempt to deemphasize intelligence, especially discrepancy notions, in conceptualizing learning or reading disabilities. To date, intelligence has received far too much consideration in defmitions of learning or reading disability, and this has diverted attention from more important variables associated with the concept of learning disabilities (Kavale, 1 993). Kavale ( 1 993) suggested that intelligence need not be a "cornerstone" variable for learning or reading disabilities. Rather it could be regarded as one among many variables that need to be considered to capture the true essence oflearning/reading disabilities.
2. 7 Conclusion
At the moment ther� is no commonly accepted criterion for identifying RD children, with identification procedures varying across researchers. This review highlights a number of issues relating to the discrepancy approach in defining RD children. The almost total reliance on discrepancy as an identification variable for reading disabilities is neither conceptually nor psychometrically justifiable for a number of reasons. First, lower IQ may be a result, rather than a cause, of reading disability (Stanovich, 1 986b ). For instance, the intelligence scores of many older children with reading disabilities are affected by their lack of success in basic school subjects because of their inability to read texts and other supplemental material (Stanovich, 1 986b; van den Bos, 1 989). This phenomenon renders discrepancy defmitions of learning and reading disabilities problematic as children grow older. Second, studies have failed to find evidence of cognitive differences between RD and garden-variety poor readers. Third, identification procedures using discrepancy as the sole criterion in identifying RD
children fail to accurately identify RD students, because discrepancy is a necessary but
insufficient criterion for determining learning or reading disabilities (Payette, Clarizio, Phillips, & Bennett, 1 995; C. R. Reynolds, 1 985a, 1 985b). For these reasons, a focus on the discrepancy criterion for diagnosing reading disabilities may not be appropriate. Such a unidimensional approach is unlikely to capture the complexity of a multivariate phenomenon like reading disability.
Instead, a multifaceted approach incorporating multidefinitional components may be a more sensible way of defining reading disability. Because reading is a complex process, taking a multidefinitional approach to defining reading disabilities is appropriate as it is more likely to capture the complexity of the construct of reading disability. A number of elements or defining features, most of which are considered fundamental indicators of the reading/learning disability concept, can be utilized in this multidefinitional approach. These elements can be determined from the common elements present across definitions (see section 2.4). Such an approach was used in the present study.
Despite the uncertainty regarding sample defmition, there appears to be some consensus regarding the primary importance of cognitive and metacognitive skills for successful academic achievement. This will be discussed in the following chapter.
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