The construct of learning disabilities (LD) has been the subject of controversy for most of its history (National Joint Committee on Learning Disabilities [NJCLD], 2010). At the extreme, some professionals question the validity of its existence, in part, because of the possible circularity of its definition as wryly stated by Lahey (1980, cited by Sun and Wallach, 2014):

Question: Why are these children with normal intelligence having difficulty learning to read?

Answer: Because they are "learning disabled."

Question: How do you know that?

Answer: Because they have normal intelligence and they are having difficulty learning to read.

Although LD is widely accepted by most professionals as a construct, there are differing perspectives regarding its definition and recommended approaches to identification/diagnosis. To help inform and advance thinking regarding the complexities of LD, we conceptualized this issue of Topics in Language Disorders as a forum for leaders from various disciplines to present and defend multiple-and sometimes competing-perspectives on the definition and diagnosis of LD. These arguments are presented within comprehensive discussions of the historical and current frameworks of language and learning theories, federal policies, and models of response to intervention/multitiered systems of support (RTI/MTSS).

In its March 2010 report developed to inform policy recommendations regarding research and practice, the NJCLD presented a number of areas of agreement and unresolved issues. There is general agreement that LD is neurobiologically based, involves cognitive processes, and affects learning. It represents a heterogeneous group of disorders that may impact one area or a combination of areas of educational performance and may coexist with other disorders. LD occurs across cultures, races, and languages, and it may also exist in individuals who are intellectually gifted. Although precursors are most often language delays or deficits in early childhood, LD persists in various forms across the life span.

The major unresolved issues as identified by the NJCLD are assessment, identification, and prevalence. This is due in large part to the complexity of the processes underlying LD. In addition, the resulting learning problems are distributed along a continuum rather than manifesting in a uniform manner. Furthermore, factors such as lack of adequate instruction or emotional problems may affect learning in a manner difficult to distinguish from the effect of LD. To date, no single method has been generally accepted as a superior means of diagnosing LD. One repercussion of this ambiguity is tremendous variability in the comprehensive evaluations used by school districts across the United States as part of the process for determining eligibility for special education services.

At the heart of the issues surrounding LD and its identification in schools is the ambiguity regarding the basic construct. From its conception, LD has been difficult to define. In this issue, Zumeta, Zirkel, and Danielson (2014) review the historical events and evolving research related to LD, from its inception as a construct to the development and evolution of special education law to the current practices around the country. This broad perspective on issues that have plagued the field in providing services to students through evaluation, identification, and intervention helps readers to properly frame the competing perspectives present in the field today.

Defining LD as a unique construct is complicated by its overlap with other constructs such as language disorders, reading disabilities and dyslexia. Could it be that LD is fundamentally a language disorder? Speech-language pathologists (SLPs) and some special educators agree that language is the basis for most, and some SLPs would argue all, LDs. Sun and Wallach (2014) propose that language disorder and LD are basically the same construct and would be better described with a combined label of language learning disability.

Both language disorder and LD occur across a continuum and present unique challenges across the age span, further adding to the complexity of definition and ultimately, identification. The notion of a continuum challenges a categorical system. In this issue, Fletcher et al. (2014) write that LD is a dimensional disorder and thus any attempts to identify subgroups show that they "are a matter of degree as opposed to identifying discrete subgroups that are different in kind" (p. x). They compare the dimensional aspects of the LD construct with obesity or hypertension, where degrees of weight and blood pressure are considered over time. Conceptualizing LD as a language disability and as a dimensional disorder allows one to think beyond current systems. Sun and Wallach (2014) suggest that LD could be identified much earlier by using knowledge about language disorders, providing a fresh perspective to address the need for early identification and intervention for LD.

Moving past issues related to defining LD, we return to the troublesome question of the best way to identify LD and design intervention. Thankfully, there is now agreement by researchers and leaders in the field that the discrepancy model is not an effective method for identification. This leaves us to consider contrasting approaches allowed by the Individuals With Disabilities Education Act of 2004 (IDEA) for identifying LD-an RTI model and patterns of strengths and weakness. Although there are different methods used in determining those patterns we will focus here on cognitive processing evaluations as a method of determining patterns of strengths and weakness. An RTI approach has been allowed by federal law for 10 years and is mandated in some states, which would suggest that we have had adequate time to answer important questions about its use. Has RTI proved to be the best process for identification? What are the advantages to the use of RTI? What procedures within the model result in the most accurate identification? Does an RTI approach alone provide sufficient diagnostic information?

Reschly provides a comprehensive overview of an RTI model. He walks the reader through the basic elements that constitute the model including

Scientifically based academic instruction and behavior interventions matched to student needs..., progress monitoring that is sufficiently frequent and sensitive to match the degree of students' needs and the intensity of the intervention, ... data-based decision making about the degree of students needs and the intensity of educational services required to meet those needs based on student progress toward benchmark goals for performance, and multi-tiered or levels of intervention that vary in intervention intensity matched to student needs. (2014, p. x)

Reschly cites Mayer, Sulzer-Azaroff, and Wallace in pointing out that "the key components at each tier (above) have a strong evidence base" (2011, p. 25). He asserts that an RTI approach is a superior means of LD identification, in part, because of its instructional relevance and because it results in improvement of special education services. Reschly says,

Despite nearly 30 years of research indicating the benefits of progress monitoring and formative evaluation to children (and teachers) (Fuchs & Fuchs, 1986; Kavale, 2007), the vast majority of current special education IEPs and programs do not use time series analysis graphs with progress monitoring and formative evaluation. These programming components enhance special education results and are more likely to be implemented after identification of SLD through RTI/MTSS because they come more or less naturally from the identification process and procedures.

There is a significant and sometimes heated debate over which elements in addition to RTI should be part of the identification process. In his article, Reschly acknowledges that RTI results should not be the only measures used to identify LD but rather are one of multiple measures needed. However, he takes a stand that cognitive processing assessment is not necessary as a part of that comprehensive evaluation. He backs up his claim by citing research that has shown negative results for interventions based on improving processes regardless of whether the "processes are conceptualized as information processing modalities (e.g., auditory, visual learners), cognitive style (simultaneous, sequential processing), or cognitive processes (memory, executive function, planning)." Even though proponents of RTI without cognitive processing evaluation generally agree that students with LD have cognitive processing problems (NCLD, 2011), they assert that evaluation should focus on intervention both preceding and following the evaluation, with a focus on achieving better outcomes (Fletcher et al., 2014; Reschly, 2014).

In the following article, Johnson (2014) promotes a contrasting, combined approach to LD identification using both an RTI model and cognitive processing assessment. Johnson argues that using RTI alone is problematic for a number of reasons. These include concerns over aspects of RTI including the need for research information about what constitutes adequate response in each area; curriculum-based measurements (CBMs) for all areas of mathematics, writing, oral expression, and listening comprehension; and that RTI is difficult to implement and monitor with fidelity. Johnson reviews research about specific cognitive processes related to each area of academics, such as phonological processing, rapid naming, and short-term memory as related to reading, and proposes that evaluation in these areas not only facilitates identification but also informs intervention. Finally, Johnson suggests that a comprehensive evaluation for LD should confirm deficits in cognitive processes as the explanation of the learning difficulties. She emphasizes that an important part of the evaluation is answering the question, "Why does this student have trouble learning?" for families.

Another issue of debate is the sequence of activities when diagnosing, identifying, and designing treatment of LD. Johnson outlines a preferred sequence to begin with implementation of RTI to narrow down the students who are suspected of having LD, followed by cognitive processing evaluation to confirm identification and inform intervention, and finally to design and provide intervention based on the results of the cognitive processing evaluation, which should incorporate assessment of such areas as working memory, phonological processing, rapid naming speed, executive function, fluid reasoning, processing speed, visuomotor production, and word retrieval. Interestingly, Johnson also lists language as a cognitive process and notes that different aspects of language should be explored for writing versus reading.

In contrast, Fletcher et al. (2014) and Reschly (2014) both assert that an advantage of an RTI approach is that intervention precedes diagnosis and that this intervention not only informs identification but, more importantly, also informs intervention planning. Fletcher et al. (2014) point out that the critical information about the student is in the context of the school setting and the student's challenges within that instruction. They recall a model for problem solving by Macmann and Barnett (1997), looking at skills needed and instructional approaches that will address problems within the context of the environment. With this perspective, Fletcher et al. (2014) present new research data related to agreement and coverage of indicators and recommend practical procedures for identification. They conclude that the comprehensive evaluation should include alternatives to a test-based-only approach and could include the CBM results, as well as a short standardized test. It is ongoing research such as this that will help the fields of language disorder and LD to continue to evolve our thinking and practices related to LD.

If Sun and Wallach (2014) are right that LD is a language disorder, this approach is consistent with the thinking in the field of child language. Curriculum-based language assessment has been a central aspect of diagnosing and planning intervention in speech-language services in schools for more than two decades (Nelson, 1989). It involves looking at the language skills needed to complete a curriculum task, how the student approaches the task, how the task could be modified, and what strategies or skills the student could learn to improve performance.

In summary, it seems that barriers exist, not only in using discrete categorical labels for LD but also in discrete but related disciplines, such as psychology, special education, and speech-language pathology. Fletcher et al. (2014) sum up this discussion saying,

One advantage of approaches to identification emanating from RTI frameworks, especially if they can be moved away from rigid cut points and psychometric criteria, is their focus on instruction and modifications of instruction as an ongoing process. In this respect, the critical question may well be need for services triggered by multiple dimensions related to treatment as an ongoing process and not as a static assessment with a single time point. (p. x)

The authors in this issue tackle the core questions of definition and assessment of LD, bringing out issues of differing definitions and understandings across and within interrelated disciplines. However, additional facets of LD remain to be examined and clarified. Issues in need of further exploration, as identified by the NJCLD at its January 2013 meeting, include the following:

* LD and English language learners: What considerations are needed when assessing? Are we adequately integrating cultural perspectives?

* Comprehensive services: The focus of intervention is generally academic performance; do we also address the social-emotional skill deficits that may accompany LD? Do we address the social-emotional impact of being identified as having LD?

* International issues: What are conceptual models of LD in other countries and other cultural contexts? What is the state of practice in both developed and developing countries?

* Adults with LD: What factors make a difference in outcomes for adults with LD? What supports are available for adults with LD who were not identified in the K-12 system or who still need assistance after graduation?

We trust that the readers of these articles will be informed and stimulated by the authors who generously shared their expertise and thinking on this controversial topic and will engage in the research needed to find answers to the lingering questions. It is our hope that ultimately our readers will respond to the challenge to advance the field to better serve individuals with LD.

-Kathleen Whitmire

-Maureen Staskowski

Issue Co-Editors

REFERENCES