The Nature of Learning Disabilities

The Nature of Learning Disabilities

G. Emerson Dickman, J.D.
Jan. 20, 2003

In 2002 the issue of Learning Disabilities as a scientifically valid concept was addressed by the Commission on Excellence in Special Education created by President George W. Bush (PCESE), the International Dyslexia Association (IDA), and by The Learning Disabilities Roundtable (the Roundtable). , These initiatives were all related. The PCESE white papers triggered the creation of the Roundtable. As a member of the Roundtable, IDA developed position papers on each of the topics for which the Roundtable sought to achieve consensus.

The following discussion appears to be the general consensus of the vast majority of the researchers, practitioners, and advocates participating in all three projects.

1. The concept of learning disability is valid.

2. The term learning disability refers to a class of specific disorders.

“There is evidence for the heterogeneity of learning disabilities” (Executive Summary p.2). The recognition that subgroups of learning disabilities exist identifies the concept of learning disabilities as a taxonomic hierarchy.

3. Such specific disorders are due to cognitive deficits.

The etiology of a learning disability is neurological in nature. A “cognitive deficit” is distinguishable from performance deficits and adaptive functions. For instance, a deficiency in phonological processing is a cognitive deficit that results in performance deficit in decoding, spelling, and fluency that predicts problematic adaptive functioning (a manifest disability) in the development of literacy skills.

In other words, a learning disability cannot be identified by reference to performance deficits or adaptive functioning alone. For instance, the ability to read at a level expected, considering age and potential, is neither necessary nor sufficient to diagnose a learning disability. On one hand, the cognitive deficit may exist even though the predictable impact on adaptive functioning has been ameliorated through effective remediation. On the other hand, problematic adaptive functioning may exist due to variables unrelated to cognitive abilities.

4. Such cognitive deficits are intrinsic to the individual.

Although it is accepted that learning disabilities are inherent, the term “intrinsic” is used in place of “congenital,” which was previously preferred, because of the currently accepted hypothesis that “environmental factors (e.g., instruction) must be in place to develop the neural networks that support academic skills,” (Executive Summary, p.7). Nevertheless, there continues to be disagreement as to whether or not a learning disability can be caused by an acquired (extrinsic) versus a developmental (intrinsic) environmental pathogen and/or postnatal trauma.

5. Such cognitive deficits are unexpected in relation to other cognitive abilities.

If the variable identified predicts the anomalous development of a particular skill, such predicted development is not unexpected. For instance, problems reading are not unexpected in light of a cognitive deficit in phonological processing. However, the deficient neurocognitive process is unexpected in relation to other neurocognitive abilities. Sally Shaywitz who has said that individuals with learning disabilities display a “weakness in a sea of strengths” aptly and simply states the concept. The concept of unexpectedness requires that the role of discrepancy analysis be considered. There is no validity to a discrepancy analysis that compares aptitude to achievement (e.g., IQ to reading ability,) or achievement-to-achievement (e.g., Math ability to reading ability).

However, discrepancy may be applied to intra-individual cognitive patterns, as a step in the identification process; which step is understood to be neither necessary nor sufficient to determine the existence of learning disability. Such an analysis merely confirms the existence of an element in the LD phenotype that distinguishes the LD child from other populations experiencing similar cognitive deficits. In other words, within the LD population individuals exhibit a pattern of cognitive deficits in the presence of a preponderance of cognitive assets. This discrepancy has diagnostic salience and is a factor that is necessary in order to help quantify appropriate expectations for intervention and establish goals relating to rate of growth. If individuals are to be grouped for instructional purposes, such information is also necessary to ensure the homogeneity of grouping.

It is the assets not the deficits that distinguish individuals with learning disabilities from other populations that share similar cognitive deficits. For instance, the individual who is considered a low achieving slow learner may have a similar cognitive profile in a particular domain to an individual with a learning disability. However, the individual with the learning disability will show a preponderance of assets relative to the deficits involved and, as a consequence, be expected to exhibit a different rate of progress and growth.

The only discrepancy model with any relevance is one that is intra-individual, compares the extent of discrepancy between cognitive deficits and a preponderance of relative cognitive assets (clinical judgment may be a significant factor in the case of a profile that is confounded by co-morbidity), and is applicable to identification, but is not a factor to be used to determine eligibility for services.

6. Such cognitive deficits predict performance deficits.

7. Such performance deficits predict consequences in adaptive functioning.

The developmental course of an unrecognized and untreated cognitive deficit is the underdevelopment of performance skills that result in a manifest disability in an area of adaptive functioning. A cognitive deficit, no matter how profound, is not a disability unless it predicts an impact on adaptive functioning. The label “disability” is not determined by the “deficit itself, but its social consequences.” (Vigotsky, 1993, paraphrase). To paraphrase Dr. Gordon Sherman, a disability is characterized by an incompatibility between biology and environment. If the skill that is impacted by the disordered variable is not needed by the culture and time in which the person exists (a contextual variable), it has no consequence and is not a disability. For instance an inability to efficiently learn to detect poisonous plants is not a disability in a culture where everyone buys their food from grocers and supermarkets. In contrast, the inability to read has significant social consequences in many cultures. We would not categorize a deficient cognitive process that predicts an inability to identify poisonous plants as a learning disability because it does not predict deficits in performance that predict consequences on adaptive functioning in the culture within which the individual is expected to perform.

8. Such consequences are variable across the life span.

Although the cognitive deficit involved is intrinsic to the individual, neurological in nature, and life-long; the consequences on adaptive functioning vary over time for a variety of reasons. For instance, the performance deficit involved, e.g., decoding, may be successfully remediated or the manifest disability, e.g., reading, is made less consequential due to life choices. For instance, one may choose to be a farmer instead of a journalist or pursue a degree in engineering instead of history.

Consistent with the foregoing discussion, the International Dyslexia Association (IDA) has proposed the following definition that identifies learning disability as a level in a taxonomic hierarchy.

The term learning disability refers to a class of specific disorders. They are due to cognitive deficits intrinsic to the individual and are often unexpected in relation to other cognitive abilities. Such disorders result in performance deficits in spite of quality instruction and predict anomalies in the development of adaptive functions having consequences across the lifespan.

To many, the forgoing discussion may seem simplistic and academic. However, the concept of learning disabilities is widely misunderstood and an ability to describe the concept with the authority of scientific consensus has powerful potential. To educators who do not understand the concept, remediation is a waste of time and accommodations are unfair. Dr. Sally Shaywitz has described the foregoing simply and accurately by indicating that, “A learning disability is a weakness in a sea of strengths.” It is this “sea of strengths” that is so often overlooked. Unfortunately, there is no learning disability, if it goes unrecognized or unremediated, that does not have the ability to pollute a child’s sea of strengths.

1 The Learning Disabilities Roundtable consisted of ten organizations sponsored by the Division of Research to Practice Office of Special Education Programs of the U.S. Department of Education. The report of the Roundtable entitled Specific Learning Disabilities: Finding Common Ground was published July 25, 2002.

2 I was privileged to have prepared the initial draft and to have lead the discussion that resulted in the IDA position paper on The Nature of Learning Disabilities, and to have been a representative from IDA to the Learning Disabilities Roundtable.