Wilson, W.J. (2018). On the definition of APD and the need for a conceptual model of terminology. International Journal of Audiology, Early online. doi: 10.1080/14992027.2019.1600057 This is a copy of the final, accepted manuscript prior to copy editing by the journal’s editorial staff. The published version of this manuscript is available at: https://www.tandfonline.com/eprint/GPziH3cPSmb7KXt6u6En/full?target=10.1080/1499 2027.2019.1600057
On the definition of APD and the need for a conceptual model of terminology
Wayne J Wilson
Corresponding author: Wayne Wilson, School of Health and Rehabilitation Sciences, The
University of Queensland 4072, Australia, [email protected]
Objective: To consider the definition of auditory processing disorder (APD). Design: Narrative review and opinion piece. Study sample: Considerations of definition drawn primarily from the fields of philosophy, audition, learning and language. Results: The problem of defining APD appears genuine.
Current and previous definitions of APD are nominal in nature, being both stipulative (offering explicit and arbitrary adoptions of meaning relation between words) and operational (creating rules that stipulate how the terms might apply to particular cases). Such definitions survive by consensus and perceived heuristic value in a manner that fails to achieve closure as arguments about their validity remain relative. Conclusion: A conceptual model of APD terminology is needed that considers nominal, conceptual and real definitions as well as different purposes for defining APD within professional and public domains. A framework for such a conceptual model of APD terminology is offered. This paper considers the definition of auditory processing disorder (APD). Types of definition are considered and applied to the definition of APD offered by the American Speech‐language, Hearing
Association (ASHA, 2005) and the American Academy of Audiology (AAA, 2010). The discussion is then expanded to more broadly consider seven questions about terminology that identify dilemmas of defining APD, the limited prospects of finding a unifying definition of APD, and the resulting need for a conceptual model of terminology for APD. The paper concludes by proposing a framework for such a model that considers both different types of definition and different purposes for defining
APD within professional and public domains. Further development of a conceptual model of terminology for APD could improve communication amongst all stakeholders seeking to help children who present with listening difficulties in the classroom. Many of the arguments offered in this paper draw directly from Kavale and Forness’s (2000) consideration of definitions of learning disabilities, Bishop’s (2014) consideration of terminology in developmental language disorders, and
Walsh’s (2005) consideration of a conceptual model of terminology for speech pathology.
Background
Even a cursory view of the research and popular literature identifies many definitions of “auditory processing disorder (APD)”. Recent definitions have split into two broad camps (Wilson, 2018). The first seeks to maintain the use of APD as a diagnostic label for deficits in the neural processing of auditory stimuli particularly in the central auditory nervous system (CANS) that are not due to higher order language, cognitive, or related factors (e.g., ASHA, 2005; Nickisch et al., 2007, AAA, 2010; CISG,
2012; Keith et al., Forthcoming). The second seeks to redefine APD or to replace it with a new term that better reflects an argument that listening difficulties more broadly are predominantly the result of deficits in neural processing of auditory stimuli due to higher order language, cognitive, or related factors (Moore et al., 2010; de Wit et al., 2016; de Wit et al., 2017).
The ongoing failure to produce a unified definition has contributed to APD lacking two critical scientific elements: understanding via a clear and unobscured sense of APD (an account of the essence of APD), and explanation via a rational exposition of the reasons why a particular child has APD (an account of the properties of APD; a demonstration of APD). Without understanding and explanation, statements about APD remain conditional in a manner that worsens rather than improves our ability to reach consensus on its definition.
Types of definition (after Kavale & Forness, 2000)
A definition is a semantic device that uses words for descriptive purposes to convey not just factual information but also meaning (Kavale et al., 1991; Kavale & Forness, 2000). Creating a definition is challenged by the need translate fundamental and basic qualities into words that are open to interpretation (Miller, 1980). Definitions are integral for developing taxonomies (Broadfield, 1946;
Kavale & Forness, 2000) by an epistemic process of naming, distinguishing, and ordering of types
(Reichenbach, 1938; Kavale & Forness, 2000). This process seeks to identify subgroups in a population (naming), decide if a particular case fits (distinguishing), and establish the degree of fit according to the available corpus of knowledge (ordering) (Korner, 1970; Kavale & Forness, 2000).
Valid and reliable taxonomies rely on definitions that comprehensively describe what is being classified.
Definitions can be broken down into many different types (Robinson, 1954; Kavale &
Forness, 2000) of which five will be considered for the purposes of the present review: real, conceptual, nominal, stipulative and operational. Real definitions are hypothesized ideals that are not often achieved as they are concerned with the properties of things in the world (Fetzer, 1991) in a manner that seeks to “account for the essence of a thing” (Aristotle, cited in Robinson, 1954).
Conceptual definitions represent sets of characteristics drawn from concepts that have been theoretically validated (as opposed to characteristics drawn only from things that have been measured) (Hempel, 1952; Kavale & Forness, 2000). Nominal definitions are concerned with words as elements of language (Fetzer, 1991) in a manner that attempts to associate words to describe something (Kavale & Forness, 2000). Nominal definitons can be further broken down into stipulative and operational definitions (Kavale & Forness, 2000). Stipulative definitions are explicit and arbitrary adoptions of a meaning relation between words that serve as requests that readers or listeners will understand words in a certain way (this makes stipulative definitions useful but does not necessarily prove them to be true) (Rantala, 1977). Operational definitions are sets of rules that describe how terms apply to particular cases (Benjamin, 1955). It might be useful to note that colloquial statements used in some western countries such as something being “true by definition” and “for the purpose of argument X, Y will be defined as …” can be seen as nominal.
Applying the types of definition described above to defining APD suggests a real definition of
APD would be one that comprehensively accounts for the essence of the thing that is APD. A conceptual definition of APD would describe the set of characteristics that define APD with each characteristic drawn from a theoretically validated concept. A nominal definition of APD would associate words to describe APD. Its stipulative component would offer explicit and arbitrary meaning relations between the words in the definition in a manner that is useful but does not necessarily prove those relations to be true, and its operational component would outline the rules for applying the words and their relations in the definition to determine if an individual person fits the nominal definition of APD.
A definition of APD: ASHA (2005) and AAA (2010)
Perhaps the most cited definition of APD in recent times is that offered by ASHA (2005) and AAA
(2010). This definition proceeds in three parts. The first broadly defines auditory processing (AP) as referring to the efficiency and effectiveness by which the CNS utilizes auditory information. The second narrowly defines AP as referring to the perceptual processing of auditory information in the
CNS and the neurobiologic activity that underlies that processing and gives rise to electrophysiologic auditory potentials; and includes the auditory mechanisms that underlie the following abilities or skills: sound localization and lateralization, auditory discrimination, auditory pattern recognition, temporal aspects of audition, auditory performance in competing acoustic signals, and auditory performance with degraded acoustic signals. The third defines APD as referring to difficulties in the perceptual processing of auditory information in the CNS as demonstrated by poor performance in one or more of the AP skills previously listed, that is not due to higher order cognitive‐ communicative and/or language related functions.
A consideration of the definition of APD offered by ASHA (2005) and AAA (2010) shows it is not real as it does not achieve a hypothesized ideal that comprehensively accounts for the essence of the thing that is APD. Nor is it completely conceptual as while it represents a set of characteristics drawn from concepts regarding APD, some of those concepts are still undergoing theoretical validation (an example here being the concept of dichotic listening as being auditory, cognitive, or both; with Cameron et al’s (2016) use of the Dichotic Digits difference Test being an example of efforts to progress the theoretical validation of the concept of dichotic listening). Instead, the definition of APD offered by ASHA (2005) and AAA (2010) is predominantly nominal as it associates words to describe APD. As a nominal definition, it is also both stipulative as it offers explicit and arbitrary adoptions of meaning relation between words that request readers to understand the words in the definition in a certain way (which makes the definition useful but does not necessarily prove it to be true), and operational as it creates rules that describe how the terms might apply to particular cases. It should be noted at this point that while other definitions of APD will not be considered here, most (if not all) are also predominantly nominal.
The nominal nature of the ASHA (2005) and AAA (2010) definition of APD presents several challenges. Its stipulative property makes it useful without necessarily proving it to be true. It then survives by consensus and perceived heuristic value in a manner that fails to achieve closure as arguments about its validity remain relative. Its stipulative property also means it must be operationalized to be applied in practice. This requires a set of operations that define the concept of
APD but prevents the definition from reaching formal status as the specified operations merely state what needs to be done to test for APD, are not easily associated with APD as a complex construct, and can lack theoretical validity in and of themselves.
Seven questions about terminology and APD (after Bishop, 2014)
To broaden discussion about the use of different labels for children with unexplained language problems, Bishop (2014) considered 10 questions about terminology in an effort to decide what term should be used to describe those children. Seven of those questions are asked here of the term
APD in an effort to broaden discussion about defining APD. It should be noted that many of the considerations offered by Bishop (2014) regarding developmental language disorder have been directly applied to the present consideration of APD.
1. Should we be concerned about APD in children?
The substantial volume of literature (both scientific and popular) dedicated to APD suggests the answer to this question is yes. Reports linking APD to poor childhood development can be found in most fields of health and education. As a result, these children are considered to be at increased risk of academic failure, behavioural and psychiatric problems, unemployment and economic disadvantage, and social impairment (ASHA, 2005; AAA, 2010; Fruhholz et al., 2016; BSA, 2017;
Moncrieff et al., 2018).
2. Should we abandon diagnostic labels?
While there appears to be agreement that we should be concerned about APD in children, there appears to be less agreement on whether these children should be given the diagnostic label of
“APD” (for a broader critique on diagnostic labels as a whole, the reader is referred to Frances
[2013]).
Proponents of APD argue it can stand alone as a diagnostic label separate to other labels such as “learning disorder”, “attention deficit hyperactivity disorder” and “developmental language disorder” (ASHA, 2005; AAA, 2010; Chermak et al., 2017). Opponents of APD argue it does not stand as a clinical entity (Vermiglio, 2014), is a questionable construct (Cacace & McFarland, 2013), is mostly irrelevant in the larger contexts of language and communication (Rees, 1973), or is a mislabel for children whose real problem has to do with cognition (Moore et al., 2010; de Wit, Visser‐
Bochane et al., 2016). Some of these authors argue for the use of broader labels such “listening deficit” (DeBonis, 2015), “children with listening difficulties” (de Wit et al., 2017), “(unexplained) listening difficulties” (de Wit et al., 2017), or “listening difficulties” (Moore et al., 2018) as more appropriate means of capturing all children with initially unexplained listening difficulties. Yet other authors argue not for the abandonment of APD as a label, but for a de‐emphasis on its use as a label in favour of a hierarchical approach to APD assessment that focuses less on defining APD and more on identifying the primary source/s of a person’s listening difficulties (Dillon et al., 2012).
Some differences in the use of APD as a diagnostic label can be seen to fall along professional lines. Within health fields, the goal of labelling children sits comfortably within medical or medical‐like models of care. This sees health professionals favour specific diagnostic labels such as
APD over broad terms such as listening difficulties. Such broad terms are thought to deny the role of biological risk factors, minimize the presenting difficulties or attribute them to poor behaviour or inadequate schooling, or hamper research by making it difficult to identify groups of children for scientific study. Within educational fields, the goal of labelling children sits less comfortably within educational models of care. This sees educational professionals favour broad terms such as listening difficulties over specific diagnostic labels such as APD that can be seen as contextually irrelevant or as having negative social consequences. In this context, such broad terms are thought to better identify children who could benefit from educational assistance.
3. Is a medical model appropriate for APD in children?
Does giving a diagnostic label, such as APD, to children inappropriately assume these children are best managed using a medical model of care?
In general, medical models consider mental disorders to be the product of biology where physical/organic factors affect brain structure and/or function (as opposed to other examples such as biopsychosocial models that consider mental disorders to be the product of biological, psychological and social factors; or recovery models that consider mental symptoms on a continuum of normal rather than as a dichotomy of normal versus abnormal). In medical models, symptoms are thought to be indicators of a physical disorder with groups of connected symptoms characterized as syndromes. Applying medical models to children with APD (and to listening difficulties more generally) faces at least four challenges. First, while physical disorders have been reported in children with APD (Musiek et al., 1985; Boscariol et al., 2010) the prevalence of these disorders in these populations appears to be low (Moore et al., 2010; BSA, 2017; Moore et al., 2018). Second, the technology needed to easily identify such physical disorders (particularly at the cellular level) is not easily applied in clinical or educational settings, is not widely available, or is lacking altogether. Third, while there is some evidence for genetic links (Morell et al., 2007; Brewer et al., 2016) or biomarkers
(Johnson et al., 2005; White‐Schwoch et al., 2015) for some AP abilities, it remains unlikely that a single genetic abnormality or syndrome or a single biomarker will be found for all APDs. Fourth, labels used within a medical model can falsely imply that a true clinical entity exists rather than simply clusters of observed or measured behaviours (Cacace & McFarland, 2013; Vermiglio, 2014). If these four challenges remain unresolved, then APD might best be conceptualized not as a disorder
(or syndrome) within a medical model, but as complex multifactorial concern probably related to varying combinations of genetic and environmental risk factors.
While problematic, medical models should not be abandoned altogether when considering children with APD. There appears to be little value in medical models that only allow for categorical disorders (or syndromes) with single causes. However, there remains value in medical models that consider biological factors as potentially affecting a child’s AP and general listening abilities (Taylor &
Rutter [2008], cited in Bishop [2014]). Such models could retain the ability to diagnose APD on the basis of test scores in cases where reduced test scores can be associated with physical disorders
(ASHA, 2005; AAA, 2010) and could allow APD to be considered as a spectral disorder if APD is deemed to include a range of linked conditions of similar appearance or resulting from the same underlying mechanism (Wilson, 2018). While the resulting diagnostic group is likely to be heterogeneous in presentation, aetiology, and prognosis, it is also likely to be homogenous for risk of further problems that could be helped by targeted intervention.
4. What are appropriate criteria for identifying APD in children?
The answer to this question will depend on the purposes of diagnosis. This can be seen in Wilson’s
(2018) description of eight historical approaches to APD and the position statements or guidelines on APD offered by 10 societies or groups from around the world. The purpose of diagnosing APD in these approaches, statements and guidelines ranged from identifying sites‐of‐lesion (or at least sites‐of‐dysfunction) in the CNS and particularly the CANS, to identifying deficient auditory behaviours and particularly those likely to affect the child’s functioning in everyday life. As a result, the criteria for diagnosing APD ranged from various numbers, types and patterns of test failure coupled with various inclusionary and exclusionary criteria; to evidence that the APD is associated with significant listening impairment in real world environments (Wilson & Arnott, 2013; Wilson,
2018). These differences were also reflected in the subsequently recommended interventions where the management of sites‐of‐lesion/dysfunction can differ substantially from the management of associated listening impairments possibly related to poor academic attainment.
5. Does it make sense to focus on “auditory” problems: is APD distinct from other neurodevelopmental disorders?
On first consideration it seems reasonable to focus on auditory problems in APD. Some authors have argued that diagnoses of APD should only be made if the problems are shown to be specific to the auditory modality (Cacace & McFarland, 2013). Yet others have argued against focusing on auditory problems in APD for at least three reasons. First, explicit modality specificity is not a feature of the human central nervous system (e.g., ASHA, 2005; AAA, 2010). Second, children with APD are more likely to present with co‐occurring difficulties across modalities than with difficulties specific to the auditory modality (Sharma et al., 2009; Tomlin et al., 2015). Third, focussing on auditory problems risks failure to fully address all needs of children with APD, particularly in the classroom.
6. What labels have been used for persons with listening difficulties?
Dillon (2018) listed (in chronological order) the following terms as having been used to label persons with listening difficulties where the terms were agnostic as to the cause of the listening difficulty: central auditory dysfunction (Berry & Blair, 1976), central auditory processing disorder (Sullivan,
1975), auditory inferiority complex (Byrne & Kerr, 1987), auditory disability with normal hearing
(Stephens & Rendell, 1988), selective dysacusis (Narula & Mason, 1988), obscure auditory dysfunction (Saunders & Haggard, 1989), central presbycusis (Stach et al., 1990), auditory dysacusis
(Jayaram et al., 1992), King‐Kopetzy syndrome (Hinchcliffe, 1992), idiopathic discriminatory dysfunction (Rappaport et al., 1993), APD (Jerger & Musiek, 2000), (central) auditory processing disorder (ASHA, 2005), and speech‐in‐noise (SPiN) impairment with a normal audiogram (Guest et al., 2018). Dillon (2018) noted that common to all of these terms was the intent to use them to describe persons with auditory perception poorer than expected from hearing thresholds in a manner that was sufficiently broad to include diverse types of deficits.
The confusion caused by the presence of so many terms is exacerbated by their potentially different meanings in different contexts. Even the recent dominance of the term “APD” continues to attract debate over each word in the term, e.g., is it auditory (Cacace & McFarland, 2013); does it concern processing or perception (Moore, 2018); and is it a disorder or a disability, impairment, delay, difficulty and/or problem (Jerger & Musiek, 2000; ASHA, 2005; Cowan et al., 2009; Dawes &
Bishop, 2009; McArthur, 2009; AAA, 2010; Vermiglio, 2014; WHO, 2016)?
7. What are the consequences of the lack of agreed terminology?
The lack of agreed terminology for describing children with APD specifically and listening difficulties generally has had multiple consequences. It has created doubt over the appropriate level of concern for these children and the models, diagnostic criteria, and labels best suited to helping them; it has hindered effective communication amongst stakeholders about these children; it has confused decisions over who is resourced for intervention; and it has prevented cumulative research as the population being studied needs to be explained and re‐explained to funding bodies who
(understandably) begin to doubt the value of funding such research. At best, this lack of agreed terminology is unsustainable; at worst it is as bad as having no terminology at all. On applying a quote by Bishop (2014) about DLD to the current consideration of APD:
Without agreed criteria for identifying children in need of additional help, and without
agreed labels for talking about them, we cannot improve our understanding of why some
children fail, or evaluate the efficacy of attempts to help them. The fact that [APD] does not
constitute a specific syndrome is not a sufficient reason to abandon labels. (pp. 392‐393).
Dilemmas of Definition (after Kavale & Forness, 2000)
Despite the many ongoing debates discussed above, Chermak, Musiek and Weihing (2017) argue considerable agreement exists among APD definitions and definers regarding the main elements of the definition of APD in ASHA (2005) and AAA (2010). Even if this statement is accepted, it provides limited comfort as ASHA (2005) and AAA (2010) (and many others) fail to provide real or conceptual definitions that answer the basic question: what is APD? Instead, they are limited to stipulative definitions that nominally define APD as being deficits in the perceptual processing of sound in the
CNS, and operational definitions that nominally define APD as being poor performance in one or more of a list of purportedly auditory skills. These limitations have allowed the specific concept of
APD to be overtaken by broad concepts such as listening difficulties in a manner that erodes the integrity of both.
The definition of APD offered by ASHA (2005) and AAA (2010) evolved primarily from the audiological and psychoeducational approaches to the disorder and the seminal investigations of
Myklebust (1955), Bocca et al. (1954, 1955) and Broadbent (1958). While both approaches to APD have origins in brain injury, the audiological approach primarily seeks to identify site(s)‐of‐lesion (or at least site[s]‐of‐dysfunction) while the psychoeducational approach primarily seeks to identify deficits in primary auditory abilities (Jerger, 2009). This creates a dilemma of definition as APD must now be defined in a manner that satisfies two different sets of paradigmatic assumptions. Further loss of meaning then occurs as the resulting definition is modified by different users to suit different applications (e.g., APD versus CAPD versus [C]APD), and/or to change emphasis from site(s)‐of‐lesion to deficient primary auditory abilities. The fact that these auditory abilities are framed as auditory processes further limits the definition as the processes now contained in the definition are themselves hypothetical constructs whose meanings also require construct validation. Other modifications such as emphasizing exclusionary criteria risk APD becoming a residual disorder or being subsumed by other disorders with similar presentations (Ferguson et al., 2011). Similarly, emphasizing discrepancy criteria, whilst being efficient and convenient, risks creating invalid inferences where children diagnosed with APD on the basis of discrepant test scores on behavioural testing are assumed to have a site(s)‐of‐lesion in the CNS despite that lesion being undocumented
(Moore et al., 2012; Vermiglio, 2016).
Prospects for defining APD: the need for a conceptual model of terminology (after Walsh, 2005)
The problem of defining APD appears genuine. Reasons for the problem are many and include the lack of real or conceptual definitions and the reliance on nominal definitions that fail to resolve issues between their stipulative and operational components. The result is existing definitions of
APD remain open to challenge and fail to explicitly answer the question, what is APD? On considering the many arguments offered above, it is doubtful and perhaps unrealistic to expect that a single, functional, universal definition of APD can be formulated. The complexities of AP and the broad scope of APD are such that attempts to impose an order on the chaotic variety of APDs are bound to be imperfect (after Walsh [2005]). If it is not possible to arrive at an agreed, single, functional, universal definition of APD, then a conceptual model of APD terminology is needed. Within such a model, Madden and Hogan (1997) argue the purpose and scope of various terms can be clarified; parameters that define the purpose of a word can be provided; adaptations for local needs can be made; and common language, reference points and data items can be related to each other.
A conceptual model for APD terminology could be drawn from a model proposed for speech pathology terminology by Walsh (2005). Walsh’s (2005) model makes a primary distinction between profession‐specific terminology for the purpose of communication within a profession versus public terminology for the purpose of advocacy, data collection and broad service planning. In this regard, purposes to be considered within profession specific terminology for APD include:
1. Diagnosis: to explain APD, provide explicit and distinctive diagnostic criteria, and to identify
true clinical entities within APD.
2. Description: to describe symptoms of APD without necessarily denoting the existence of a
clinical entity, and to develop professional understanding of APD.
3. Research and tentative clinical labels: to allow researchers to label groups of subjects for
exploratory research (with care needed to avoid such terms being used as diagnostic labels
as in the case of the heavily and justly criticised use of “suspected APD” or “at‐risk for APD”
to group persons with listening difficulties of unknown origin).
4. Discredited clinical labels: to identify APD terminology which is clearly not useful.
The purposes to be considered within public terminology for APD include:
1. Service delivery: to group individuals with APD for services and to increase understanding
about the general needs of persons with APD. Provides a ‘‘handle’’ to compete for funds for
APD within the service sector. Is not a clinical label.
2. Lobbying and advocacy: to delineate persons with APD in order to advance their needs and
rights. Provides a “handle” to lobby for resources and to redress misunderstandings about
APD in society. Takes the perspective of the client. 3. Politics and legislation: to represent people with APD in legislation, national population
statistics, and social planning. May necessitate a range of terms across different regions.
The significant reset provided by a conceptual model of APD terminology could place APD back into a pre‐paradigmatic period where any and all concepts are appropriate and justified in delineating its parameters. These concepts can then be systematically debated in an attempt to build a comprehensive and unified conceptual structure that better answers the question, what is
APD? Kavale and Forness (1995) suggest two steps as being particularly important in this process: 1)
Formulate foundation principles using a conceptual process that aims to develop a theoretical framework for viewing the nature of APD (the validity of which it tested at a later date), and: 2)
Develop an operational definition of APD that is more concrete than abstract stipulative definitions, but need not be limited by an over‐emphasis of discrepancy criterion as the major operationalized factors (i.e., not be limited by an over‐emphasis on the need to demonstrate a discrepancy between expected and actual AP abilities as the means of operationalising a definition of APD).
A framework for building a conceptual model for APD terminology
Table 1 shows a proposed framework for building a conceptual model for APD terminology that both considers different types of definition and different purposes for defining APD within professional and public domains. This table also proposes terms for possible use within each level of the framework, as well as terms that could be excluded from the framework.
Operational definitions are to be presented at three levels, each representing a possible decision point on the path towards diagnosing APD. Level I would seek to document an ability‐ achievement discrepancy that is a necessary but not a sufficient criterion for APD identification. It would use broader terms such as “unexplained listening difficulties” to label children presenting at this level. Level II would seek to address possible associations between listening and psychological process deficits. It would use slightly narrower terms such as “listening difficulties” to label children reaching this level. Level III would seek to introduce exclusionary clauses with the goal of offering the best explanation for the poor performance on tests of listening by eliminating other disorders to leave APD as the primary designation, identifying APD and other disorders to offer APD as being associated or co‐existing with those disorders, or identifying other disorders as the primary designation. It would be the first to use the term “APD” to label children reaching this level although its definition of APD would remain operational.
A stipulative definition would follow the above operational definitions to more specifically describe APD and its symptoms without necessarily denoting the existence of a clinical entity. It would allow for more explicit and distinctive labelling of children with the term “APD” whilst still allowing the disorder to be associated or co‐exist with other disorders.
A conceptual definition of APD would rely on the identification of true clinical entities within
APD that could be explicitly and distinctively labelled as such within the conceptual boundaries of the definition. One such boundary would be the need for the clinical entities to be theoretically validated. Currently, possible candidates for clinical entities within APD suggested in the literature include speech‐in‐noise disorder (Vermiglio, 2014), spatial processing disorder (Cameron et al.,
2014), amblyaudia (Moncrieff et al., 2016), and speech‐in‐noise (SPiN) impairment with a normal audiogram (Guest et al., 2018). These terms are candidates for consideration only. Ongoing debate about their validity as clinical entities is noted.
Finally, the above series of definitions of APD would seek to progress towards a real definition that comprehensively explains APD as a theoretical construct and provides a taxonomy for naming , distinguishing and ordering APD types (and/or clinical entities). Such a real definition would need to be acceptable across professional and public stakeholder groups interested in helping children with APD.
Conclusion
This paper considered the definition of auditory processing disorder (APD) by way of the different types of definition, the definition of APD offered by ASHA (2005) and AAA (2010), seven questions about terminology, and the need for a conceptual model of terminology. A framework for such a conceptual model of APD terminology was then offered. This model represented a departure from previous approaches to defining APD that had started with stipulative definitions that were then operationalised for particular contexts at the expense of conceptual or real definitions.
Conceptual models of APD terminology are needed if we are to achieve a clear and unobscured sense of what is APD so that we can better explain (via rational exposition) why some children have this disorder.
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Language, and Hearing Research, 56, 63‐70. Type & nature of definition Main purpose Parameters Terms suggested for use by the author Progression of terminology Operational (Nominal): set of rules stipulating how terms From listening apply to particular cases. difficulties ‐ Level I: underachievement. To document ability‐achievement Professional & public: Describes ‐ Unexplained listening difficulties. An ability‐achievement discrepancy possibly related to experience & implications for the discrepancy possibly related listening difficulties. child. to listening difficulties. ‐ Level II: poor performance To address possible associations Professional: explicit & distinctive ‐ Listening difficulties. on tests of listening involving between listening & criteria to group observed ‐ Other terms as appropriate if primary designation is audition, attention, memory, psychological process deficits. behaviours. clearly other than auditory, e.g., ADHD, ASD, DLD, &/or &/or language. Public: Criteria to group children memory disorder. for provision of services. ‐ Level III: best explanation To include exclusionary clauses to Professional & public: explicit & ‐ APD: if primary designation is auditory. for poor performance on identify other conditions & allow distinctive criteria to label a child as ‐ APD associated with other disorder: if auditory tests of listening involving the identification of an APD as a having an APD. designation clearly associated with other audition, attention, memory, primary, associated, co‐existing designation/s, e.g., APD associated with brain injury, &/or language. or inappropriate designation. syndromes, &/or ANSD. ‐ APD co‐existing with other disorder: if auditory designation co‐existing with other designation/s, e.g., APD co‐existing with ADHD, ASD, DLD, &/or memory disorder. ‐ Other terms as appropriate if primary designation is other than auditory, e.g., ADHD, ASD, DLD, &/or memory disorder. Stipulative (Nominal): explicit To develop understanding of Professional: explicit & distinctive ‐ APD. & arbitrary adoptions of a APD. Describe APD & its criteria to label a child as having an meaning relation between symptoms without necessarily APD. words. denoting the existence of a clinical entity. Conceptual: characteristics To explain APD, provide Professional: explicit & distinctive ‐ To be determined pending validation of clinical drawn from theoretically diagnostic criteria, & identify true criteria to diagnose a child as entities within APD. validated concepts. clinical entities within APD. having an APD. Real: a hypothesized ideal. To comprehensively explain the Professional: criteria for developing To be determined pending professional & public construct of APD. a taxonomy by an epistemic acceptance of a validated APD construct. To APD process of naming, distinguishing & ordering of types.
Terms suggested by the author to be abandoned (if not so already) as not being useful to ongoing considerations of APD: central auditory dysfunction, auditory inferiority complex, selective dysacusis, obscure auditory dysfunction, central presbycusis, auditory dysacusis, King‐Kopetzy syndrome, idiopathic discriminatory dysfunction, suspected APD, and at‐risk for APD. Terms suggested by the author to be abandoned to lessen confusion over the term APD: CAPD, (C)APD and hidden hearing loss.
Table 1: a proposed conceptual model of APD terminology. Note: ANSD = auditory neuropathy spectral disorder, ASD = autism spectrum disorder, DLD = developmental language disorder.