In 1963, the American psychologist and educator Samuel Kirk announced that he had coined the term ‘learning disabilities’ to refer to the academic difficulties exhibited by some children in the absence of intellectual disability, or sensory impairments. Fifty years on, it is timely to reflect on what we have learned, and what more we need to understand to better assist children with learning problems.
Over the past decade, we have witnessed significant advances in the definition and classification of learning disorders, in our understanding of the cognitive, neurobiological and genetic features, and in best practice in assessment and intervention. We now have a broad theoretical framework which integrates research findings in cognition, neurodevelopment, genetics, test development and educational methods.
Despite this progress, contemporary practice in the field continues to be hampered by a lack of understanding among psychologists and other professionals of the nature, identification and treatment of learning disorders. In part, this reflects the ongoing influence of historically popular but unsupported theories and practices, which may itself reflect deficiencies in knowledge and skills attributable to gaps in psychological education and training.
This article aims to provide an overview of contemporary thinking in the field of learning disorders, identifying some shortfalls in popular approaches and focusing on developments in diagnosis and classification, theory, assessment and interventions. For the purposes of this article, the terms ‘learning disabilities’ and ‘learning disorders’ will be treated as synonymous, as, even though some researchers and clinicians propose that the terms be applied to differing presentations of academic skills deficits or cognitive profiles, there is little unanimity in usage.
Diagnostic and classification issues
Clinicians have long been interested in individual differences in cognitive functioning, with early descriptions focussing on the patterns of preserved and impaired cognitive functions displayed by individuals following acquired brain injuries. From the late nineteenth century, attention was increasingly paid to those who, despite no history of acquired injury, nevertheless displayed marked differences in their cognitive skills. Prominent in this work were descriptions of children who were unable to read, despite the provision of appropriate educational opportunities, and who did not display a low level of general intellectual functioning. This unexpected problem in learning to read was soon presumed to result from a congenital and probably inherited biological dysfunction involving one or more undetermined regions of the brain. It was also evident to early investigators that these children did not respond to typical education methods.
Subsequently, studies examined children who displayed marked problems in skills other than reading, including spelling, mathematics, or language comprehension and production. While problems in this broader range of academic skills were viewed as conceptually similar to those in reading, it was not until Kirk’s 1963 conference paper that the term ‘learning disabilities’ was proposed to refer to the group of children with ‘unexpected’ difficulties acquiring basic academic skills. As he emphasised, the problems of children with these learning disabilities were understood to be distinct from those with intellectual disability, perceptual problems or other well-recognised conditions. Fifty years on, the term is still used to characterise conditions marked by deficits in academic skills, which are not explained by a low level of general intellectual functioning, the lack of educational instruction, or the presence of emotional or behavioural problems which have interfered with learning.
Traditionally the list of learning disorders has been proposed to include reading disorder (dyslexia), mathematics disorder (dyscalculia), and disorders of written expression. Some frameworks have included developmental language disorder (specific language impairment) as a further diagnosis within learning disorders. Ultimately, the issue of which conditions are to be included under the ‘umbrella’ term of learning disorders is unimportant in the clinical context. As defined by a specific deficit in academic skills, learning disorders may be viewed as a subset of the broader category of disorders of cognitive functioning primarily attributable to neurodevelopmental causes, which includes intellectual disability, attention-deficit/hyperactivity disorder, autism spectrum disorders, and specific language impairment, in addition to the well-recognised reading, spelling and writing disorders. The difference between the traditional learning disabilities and other developmental cognitive disorders is that the latter are usually defined in ways other than by reference to academic skills deficits.
While there may seem to be as many classification systems for learning disorders as there are researchers in the field, there is general agreement that disorders must be defined and delineated on the basis of careful consideration of internal consistency and external validity, including examination of aetiology, pathology, course and response to treatment. The application of these criteria results in the recognition that several commonly encountered purported conditions lack internal or external validity, either due to the absence of a coherent theoretical account of its nature, aetiology or cognitive profile, or by being not clearly differentiated from other, well-validated disorders. Examples of such proposed conditions include central auditory processing disorder, sensory integration disorder, and scotopic sensitivity syndrome. Identifying these conditions as unvalidated does not imply that individuals with such diagnoses do not have significant difficulties, but it affirms that the learning problems would be better understood from the perspective of a taxonomy with clear theoretical and empirical support. That the diagnoses we use are validated is essential for effective practice: a child who is labelled with or treated for one of these unvalidated disorders is at risk of not receiving the appropriate intervention which would follow from a recognised diagnosis.
Modern theoretical approaches to learning disorders have integrated findings in genetics, neurobiology, cognitive psychology, development and teaching practices into a systematic account of the academic skills deficits observed in children and adults.
The major focus of research has been the identification of the specific cognitive deficits hypothesised to be the primary causal factors in learning disorders. In the area of reading disorders, for example, deficits in phonological processes have been identified for several decades as a common characteristic, with the severity of these deficits generally predictive of the severity of the reading impairment. However, the development and use of academic skills has also been recognised to be affected by a range of behavioural, emotional and motivational factors, including anxiety, depression and behavioural inhibition. These factors interact with the cognitive processes: they impact on the development and application of cognitive skills, and are in turn exacerbated by cognitive deficits. Other areas of research examine genetic and neurobiological factors associated with learning disorders, and the contribution of the learning environment to the presence and severity of specific disorders.
This research has led to an increasing recognition of the complexity of the field, which challenges the older view that learning disorders are amenable to a simple classification into clearly differentiated diagnostic categories, and that each type may be explained by a deficit in a discrete area of cognitive functioning. On the contrary, it is now believed that learning disorders result from the interaction of multiple genetic and environmental factors, which affect the development of the neural systems mediating certain cognitive processes necessary for the attainment of academic skills. These genetic and environmental factors are shared among several different developmental cognitive disorders, and it is possible that no one factor is necessary or sufficient for the emergence of a particular condition. In this new model, types of disorders are not discrete categories, but reflect quantitative differences on multiple aetiological, neurobiological and cognitive variables. The multifactorial model fits well with the established view that a disorder such as dyslexia does not represent a clearly distinct manner of reading, but rather represents the lower end of the normal continuum of reading abilities. It also accords with observations regarding both the heterogeneity of learning disorders – the variability in symptoms in a particular condition – and their frequent comorbidity.
The multifactorial approach may be illustrated by the example of dyslexia. While it is well established that a deficit in phonological skills is a key feature of a reading disorder, it is evident that some children exhibiting marked difficulties with speech sounds do not manifest poor achievement in reading, indicating that factors other than phonemic awareness must be playing a part. One theory is that a second deficit in speeded naming must be present to cause dyslexia; if absent, the phonological deficits are evident in oral speech, but do not result in marked reading impairment.
As noted above, learning disorders have long been associated with the presumption of unexpected underachievement: the child is displaying academic skills at a level below that expected for age, intelligence and opportunity. Therefore, accurate diagnosis requires: (1) evidence of poor performance on tasks assessing academic skills; (2) demonstration of inadequate response to age-appropriate instruction; and (3) exclusion of explanatory factors, such as a low level of intellectual functioning, visual or auditory deficits, or behavioural or emotional problems judged to have hampered participation in learning.
The first of these diagnostic criteria is addressed by the administration of a measure of academic skills with appropriate standardisation, normative data and psychometric properties. The second criterion requires that there be evidence of a lack of response to appropriate efforts to improve skills. While the incorporation of evaluation of response to intervention (RTI) as a step in diagnosis is sometimes seen as a new idea, in fact it reflects a fundamental element in learning disorder definitions over several decades, albeit one which has been too often ignored in practice.
The third of the diagnostic criteria for learning disorder requires that alternative explanations for poor academic skills be systematically considered and excluded. Sensory deficits and a lower general intellectual functioning are obvious possible causes of low achievement, and so these hypotheses must be carefully tested. Behavioural, emotional and social problems, motivation, and family and school environment all contribute to learning, and so these must also be assessed and evaluated.
In sum, diagnosing a learning disorder is not accomplished solely by observing poor performance on a test of academic skills; it also requires assessment of broader cognitive functioning, and examination of a range of individual and environmental factors.
A comment on the use of intelligence tests is warranted. The second criterion required for accurate diagnosis of a learning disorder emphasises that assessment of intelligence is conducted to test the hypothesis that generally low functioning may be a cause of poor academic skills. While the exclusion of low intelligence was traditionally operationalised by the calculation of the discrepancy between intelligence and achievement (with only those manifesting a significant discrepancy being viewed as learning disordered), a wealth of theoretical and methodological problems with this notion have led to its abandonment as a diagnostic criterion. For example, discrepancy approaches implicitly assume that the reading problems of poor readers with an average or higher IQ differ from those of lower intellectual abilities in terms of the aetiology of their reading problems, the underlying cognitive processes, or in response to intervention. However, studies over several decades have failed to support these assumptions. It is now accepted that the discrepancy approach lacks external validity, either with cognitive factors or with response to interventions, and should not be employed in contemporary practice.
Following the above criteria for diagnosis of a learning disorder, psychological assessment practice should always include the systematic assessment of achievement, general intellectual functioning and psychosocial functioning. It is clearly insufficient to limit psychological testing to the administration of either an intelligence battery or achievement testing alone. Where mandated, encouraged or accepted by educational systems, this limited assessment approach promotes and entrenches demonstrably inadequate practice.
Over the past decade, the advances in understanding learning disorders have led to an expansion of research into theoretically-based interventions for learning disorders, with promising findings in both treatment and prevention, especially with regard to dyslexia. This has enabled clinicians to build upon existing techniques and to tailor these more effectively for children with specific patterns of academic deficits. This has been most evident in the prevention and treatment of dyslexia, where by identifying the pattern of deficits in word recognition, fluency and comprehension, interventions have been targeted more precisely to the needs of the individual child. Thus interventions for children with word recognition or fluency difficulties primarily involve instruction and training in orthographic patterns, progressing from the alphabetic to sublexical levels, embedded within activities designed to enhance knowledge of the meaning and use of words and morphemes. In contrast, children whose reading problems are primarily in the comprehension of text benefit more from the inclusion of instruction in identifying and utilising metacognitive strategies as a major component of treatment.
Unfortunately, a feature of current practice in the field of learning disorders is the continuing popularity of methods which do not have demonstrated efficacy in outcome studies, or which have been tested and found to be ineffective. These include a diverse range of sensory and motor approaches, including sensory integration therapy, sound therapies, visual methods and exercise therapies, as well as methods aimed at purported cognitive preferences or styles. Such interventions have been shown to be inconsistent with contemporary theories of the cognitive and neurobiological deficits in learning disorders, and are promoted and sold without evidence for their efficacy.
The continued use of these unvalidated methods may be assumed to be a consequence of a lack of current knowledge of the nature and treatment of learning disorders among parents and professionals. It also no doubt reflects the absence of government regulation of practice in this field. Although the Australian Competition and Consumer Commission has taken action in recent years against proponents of purported treatments of allergies, snoring and impotence, on the basis that the claims of efficacy were made with little or no supportive scientific evidence, there has yet to be investigation of those educational methods for which evidence is limited to anecdotes, testimonials and/or methodologically unsound reports. In the meantime, the obligation to eschew unvalidated methods rests with the practitioner responsible for providing the best possible care for clients.
Given the progress of the last ten years, it may be expected that we will see further integration of research in diverse fields, including academic skills, cognitive deficits, genetics and neurobiology, and more explicit models of the interaction of multiple risk factors in the development and expression of learning disorders.
There is a clear need for the articulation of standards of practice for the assessment and diagnosis of learning disorders, and for the selection and implementation of interventions. We now have a strong body of knowledge from which to derive evidence-based practice in assessment, and we need to ensure that this is both employed by practitioners and supported by the policies and practices of educational authorities. We also understand which interventions are evidenced-based, with strong, demonstrated empirical support for their effectiveness.
Children with learning disorders, their parents and their teachers are entitled to expect that educational institutions, psychologists and other professionals are able to provide sound, accurate and useful advice. However, as noted above, progress will be hampered by the propensity to hold on to historically popular but unsupported theories and practices. It is critical that psychologists practising in this field address any deficiencies in knowledge and skills in order to ensure competent practice. New discoveries require practitioners to abandon older and simpler conceptions of the nature and aetiologies of learning disorders, and to accept that this complexity is necessary for an informed understanding of the field, for accurate diagnostic assessment, and for the design and implementation of effective interventions.
In time, education and health professionals will come to adopt a consistent terminology and taxonomy – but this will first require widespread recognition of the complexity, heterogeneity and comorbidity of learning disorders, and this in turn requires general acceptance of the need to base practice in science. With our training in cognition, neurobiology and assessment, psychologists are ideally placed to lead the way in assisting other professionals and educational authorities to improve their understanding and practice, by articulating a theoretically and empirically informed understanding of the nature of learning disorders, employing assessment practices that reflect advances in the science of learning disorders, and utilising or advocating for interventions with demonstrable efficacy.
The author can be contacted at firstname.lastname@example.org.