The Importance of Modality Specificity in Diagnosing Central Auditory Processing Disorder

Point/Counterpoint Article The Importance of Modality Specificity in Diagnosing Central Auditory Processing Disorder Anthony T. Cacace Albany Medical College, Albany, NY Dennis J. McFarland Wadsworth Laboratories, New York State Health Department, Albany Purpose: This article argues for the use of processes from more generalized dysfunction; modality specificity as a unifying framework by it lacked discriminant validity and resulted in which to conceptualize and diagnose central an incomplete assessment. Consequently, any auditory processing disorder (CAPD). The intent hypothetical model resulting from incomplete is to generate dialogue and critical discussion assessments or potential therapies that are in this area of study. based on indeterminate diagnoses are them- Method: Research in the cognitive, behavioral, selves questionable, and caution should be and neural sciences that relates to the concept used in their application. of modality specificity was reviewed and Conclusions: Improving specificity of diag- synthesized. nosis is an imperative core issue to the area Results: Modality specificity has a long of CAPD. Without specificity, the concept has history as an organizing construct within a little explanatory power. Because of serious diverse collection of mainstream scientific flaws in concept and design, the unimodal disciplines. The principle of modality specificity inclusive framework should be abandoned in was contrasted with the unimodal inclusive favor of a more valid approach that uses framework, which holds that auditory tests modality specificity. alone are sufficient to make the CAPD diagnosis. Evidence from a large body of data demonstrated that the unimodal framework Key Words: central auditory processing was unable to delineate modality-specific disorder, modality specificity ew discoveries, technical innovations, and novel review process is not perfect, it has stood the test of ideas are some of the driving forces behind the time and remains an important element in establishing N advancement of science. A key building block in the credibility of any form of scientific inquiry. As part this process is the interchange of information. Information of scientific inquiry, information evolves through various exchange allows for debate, discussion, and, in many stages of development: from the idea stage, to the instances, resolution of often contentious and highly experimental stage, to the consensus stage, and ultimately charged issues, so that new ground can be broken and to the knowledge stage. Attainment of the knowledge stage science can progress. Common modes of interchange of development means that the idea has been accepted and include podium and poster sessions at scientific meetings, validated. Although reaching the knowledge stage is time- publications in peer-reviewed journals, books, book and labor-intensive, obtaining convergence by multiple chapters, magazine and newspaper articles, and, most independent investigators is worth the effort. Validation recently, postings on the Internet. Publication in peer- therefore remains an important final hurdle to be reviewed journals is considered the hallmark of scientific surmounted before new constructs can be introduced into information exchange, in large part because peer review by science (Campbell & Fisk, 1959). Consequently, when the experts in the field is a sine qua non for demonstrating the knowledge stage is reached, the boundaries of the archival quality of work and the novelty of ideas. Although the peer literature expand and the historical record adds another 112 American Journal of Audiology Vol. 14 112–123 December 2005 A American Speech-Language-Hearing Association 1059-0889/05/1402-0112 element to its repository from which to build upon. It is at apparent (or at least should be manifest to a lesser degree) this point in the scientific process that information can be when similar types of information are presented to other broadly disseminated so that society at large can benefit sensory modalities. Therefore, CAPD should be distinguish- from this achievement. Clearly, this is a dynamic process able from cognitive, language-based, and/or supramodal that continuously evolves as new information is incorpo- attentional problems in which modality-specific perceptual rated into the knowledge base. dysfunctions are not expected. Following this logic, we define Although books have been written, committees have been CAPD as a modality-specific perceptual dysfunction that is formed, and consensus conferences have been convened, not due to peripheral hearing loss.1 However for this approach central auditory processing disorder (CAPD) has not reached to be effective, multimodal testing is necessary. This requires the knowledge stage of development. In our view, this area of an orientation for assessment of CAPD that is different from inquiry has stalled somewhere between the experimentation what is commonly employed. Although there are other and consensus stages of development. This state of affairs is a approaches to CAPD diagnosis, we believe that this is the dual-edged sword: On the positive side, it offers a unique simplest and most direct to implement clinically. We also opportunity for researchers to study and refine this topic; emphasize that this position does not exclude the possibility of however, for clinicians, educators, and students, it is modality-specific linguistic or nonlinguistic processes, atten- problematic because in many instances the information tion, memory, and so on (McFarland & Cacace, 1995b).1 content currently found in books offers a dubious represen- The rationale for adopting modality specificity as a tation of how CAPD should be conceptualized and diagnosed. criterion for diagnosing CAPD is based on the assumption that The stalling of the field at this stage of development also any given test can be affected by multiple factors (Cacace affects how students are taught and how clinicians are trained. & McFarland, 1998; McFarland & Cacace, 1995b). For Related issues, such as management and treatment of CAPD, example, even a simple detection experiment can be viewed are often discussed, but validated models do not yet exist. as reflecting multiple factors. Signal detection theory (Green Indeed, books and book chapters that have been written on this & Swets, 1974) holds that the subject’s behavior is a joint topic are still based largely upon ‘‘expert opinion.’’ In the function of sensitivity to the physical stimulus and a present health care environment, where evidence-based subjective criterion. The utility of this distinction has been medicine is becoming the standard of care, policy decisions demonstrated by showing that the detection of a stimulus in based on expert testimony alone do not carry the same weight noise is influenced by factors such as monetary contingencies. that they once did. This holds true for evaluation and treatment This illustrates that there is not a one-to-one correspondence and for third-party reimbursement. between a subject’s behavioral response and sensitivity to a In sum, there are many issues of contention and general specific stimulus. More complex ‘‘sensitized’’ tests, often lack of agreement on various topics in the area of CAPD, due used in CAPD assessment, introduce the potential for in large part to reliance on expert opinion rather than on additional factors to influence performance. Indeed, factors controlled experiments. Testing paradigms used by many in such as attention, motivation, and the complexity of the motor this field are similar to those proposed more than 50 years ago. response may not involve central auditory mechanisms. One Therefore, it can be argued that ideas and beliefs that are still way to evaluate the impact of such supramodal processes is to used to characterize the area of CAPD have outlived their systematically vary the nature of the stimulus while holding usefulness. This apparent unwillingness to accept change all other factors constant. For example, discrimination has contributed to the area of CAPD becoming stagnant and performance on auditory frequency pattern tasks can be has thwarted its development such that the field has not contrasted with discrimination performance on visual color- progressed in any meaningful way. Our interest is to change pattern tasks (e.g., Cacace, McFarland, Emrich, & Haller, this position and redirect research efforts in a positive 1992; McFarland & Cacace, 1997). If reduced performance direction. The concept and application of modality specificity is due to auditory-specific processes, then the deficit seen is one way to achieve this goal and to allow for the area of on acoustic versions of the task should be greater than that CAPD to move forward. seen when other stimulus modalities are used. In this way, dissociation between performances on parallel versions of a task using different stimulus modalities can be established. Modality Specificity as a Criterion for Diagnosing CAPD: The Underlying Logic 1This position is concordant with the definition of CAPD originally proposed by McFarland and Cacace (1995b) and one that was embraced In order for specific topics to be studied with precision and by participants involved with the Bruton Consensus Conference, ca. 2000 rigor, it is important to have a definition that is unambiguous (Jerger & Musiek, 2000, p. 468). The Bruton Consensus Conference also and straightforward, one that allows hypotheses to be tested suggested that use of the term CAPD be replaced with

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