Empirical and Theoretical Support for Direct Diagnosis of Learning Disabilities by Assessment of Intrinsic Processing Weaknesses

Joseph K. Torgesen, Florida State University
Learning Disabilities Summit: Building a Foundation for the Future White Papers

This paper is available in alternative formats: | Download Word | Download pdf |

Pages: | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |

ADVANTAGES OF A PROCESSING APPROACH TO DIAGNOSIS OVER CURRENT DISCREPANCY-BASED APPROACHES

If it were possible to reliably identify children with learning disabilities by directly assessing their intrinsic processing weaknesses, advantages over current aptitude-achievement discrepancy approaches would be apparent in three areas. First, it would allow identification of the learning disability very early in the instructional process so that preventive, rather than remedial, instruction could become the norm. We now know a great deal about the negative consequences to children of serious academic failure during the early years of schooling (Cunningham & Stanovich, 1998; Kistner & Torgesen, 1987; Stanovich, 1986), and discrepancy approaches to diagnosis require the child to show significant failure in basic academic subjects before the diagnosis can be made. Recent evidence (Torgesen, Rashotte, & Alexander, 2001) suggests that the costs of waiting to intervene for children who have serious reading disabilities may be enduring difficulties in reading fluency that are extremely difficult to overcome.

A second advantage of process assessment, or primary diagnostic, approaches over discrepancy-based approaches is that they will not arbitrarily exclude children from receiving instruction that is appropriate to their educational needs. For example, discovery of the core phonological problems associated with specific reading disability has had at least one unanticipated consequence. The ability to assess these core language problems directly has led to the discovery that the early word reading difficulties of children with relatively low general intelligence are associated with the same weaknesses in phonological processing that interfere with early reading growth in children who have large discrepancies between general intelligence and reading ability (Fletcher et al., 1994; Share & Stanovich, 1995; Stanovich & Siegel, 1994). This discovery is consistent with recent reports from intervention studies that general verbal ability does not predict growth in early word reading ability when differences in phonological ability are controlled (Torgesen et al., 1999; Vellutino et al., 1996). It is also consistent with findings that discrepant (IQ higher than reading ability) and non-discrepant (IQ similar to reading ability) groups show a similar rate of growth in word-level reading skill, both during early elementary school (Foorman, Francis, Shaywitz, Shaywitz, & Fletcher, 1997) and into early adolescence (Francis, Shaywitz, Stuebing, Shaywitz, & Fletcher, 1996).

Thus, to exclude children from special instruction designed to help them acquire good word-level reading skills because their reading ability is not significantly discrepant from their general intelligence level fails to recognize that they have the same learning handicap as children who score higher on tests of general intelligence. The learning handicap in both cases involves weaknesses in phonological processing ability. Children with this particular handicap respond equally well to explicit and intensive instruction in phonological awareness and phonemic decoding skills, regardless of their level of general intelligence (within the broadly "normal" range) (Torgesen et al., 1999).

The final potential advantage of an approach to diagnosis involving identification of basic processing weaknesses involves benefits for instruction. If we had full understanding of the component processes and knowledge required to perform specific academic tasks, and we could measure these component processes and knowledge accurately in children, this would be of enormous potential benefit for instruction. An example from the research on reading disabilities can serve to illustrate this potential in two ways.

Although we have already acknowledged that measures of phonological awareness do not directly assess an intrinsic processing disability, they do assess a kind of knowledge about phonemes and an ability to process them in specific ways that is causally related to ability to acquire alphabetic reading skills. Children who cannot successfully perform simple measures of phonological awareness in kindergarten are highly likely to experience difficulties learning to read (Wagner et al., 1997). There is also a powerful convergence of evidence (National Reading Panel, 2000) that special attention to stimulating phonemic awareness in young children (particularly those who have weaknesses in this area) helps them to learn to read more easily. Although instruction to build phonemic awareness does not necessarily remediate children's intrinsic weaknesses in phonological processing, it does help them to acquire a specific kind of knowledge and skill required in learning to read. So, even if a fundamental processing weakness is not directly remediable, knowing about its presence in specific children may direct our attention to the need for special and/or sustained instruction to build the specific reading or pre-reading skills that the processing weakness makes it difficult for the child to acquire.

An even more dramatic, albeit still speculative, approach to direct intervention for children's processing weaknesses is illustrated in the work of Tallal and her colleagues (Tallal et al., 1996; Merzenich et al., 1996). These investigators have reported success in directly modifying children's ability to process the rapidly changing or rapidly successive features of auditory signals. In effect, they claim to have a technique that can change the way the brain processes speech, and other auditory signals, so that perception and understanding of speech and language is improved. These effects have been documented primarily for language comprehension in children with severe language disabilities, but some evidence has also been reported that the method can lead directly to improvements in phonemic awareness (DeMartino, Espresser, Rey, & Habib, in press; Habib et al., 1999). This latter finding is consistent with the idea that the method may have some use in treating the core information processing deficits of children with developmental dyslexia. Because negative results for this method and its theory are also being reported (cf. McAnally, Hansen, Cornelissen, & Stein, 1997; Mody, Studdert-Kennedy, & Brady, 1997; Nittrouer, 1999), its applicability as a widely useful intervention technique for children with reading disabilities is still uncertain. Although the field of learning disabilities is rightfully wary of instructional methods that claim to affect basic processing capabilities and thus to improve academic learning outcomes (Hallahan & Cruickshank, 1973; Hammill & Larson, 1974; Torgesen, 1979), we must remain open to genuine scientific achievements that may be powerfully beneficial to many children.

SUMMARY

Direct diagnosis of the processing weaknesses of children with learning disabilities has three important advantages over IQ-discrepancy approaches. First, a processing approach to diagnosis would not require that the child endure a period of failure in school before the diagnosis was made. This would encourage early intervention and prevention of learning difficulties so that many of the effects on learning attitudes and lost opportunities for academic growth that are the result of failure could be avoided. Second, direct assessment of processing weaknesses would allow instruction to be targeted to all children who have common learning handicaps, and not just to those who satisfy an arbitrary discrepancy criterion. Finally, identification of children's intrinsic processing weaknesses has the potential, at least, to help focus instruction in areas of greatest need.

Pages: | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |

Return to LD Summit papers table of contents