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Hammill Institute on Disabilities

Operational Definitions and Learning Disabilities: An OverviewAuthor(s): H. Lee SwansonSource: Learning Disability Quarterly, Vol. 14, No. 4, Operational Definitions and LearningDisabilities (Autumn, 1991), pp. 242-254Published by: Sage Publications, Inc.Stable URL: http://www.jstor.org/stable/1510661 .

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OPERATIONAL DEFINITIONS AND LEARNING DISABILITIES: AN OVERVIEW

H. Lee Swanson

In 1981, the National Joint Committee for Learning Disabilities (NJCLD) adopted the fol- lowing definition:

Learning disabilities is a generic term that re- fers to a heterogeneous group of disorders manifested by significant difficulties in the ac- quisition and use of listening, speaking, read- ing, writing, reasoning, or mathematical abili- ties. These disorders are intrinsic to the in- dividual and are presumed to be due to central nervous system dysfunction. Even though a learning disability may occur concomitantly with other handicapping conditions (e.g., sen- sory impairment, mental retardation, social, or emotional disturbance) or environmental influ- ences (e.g., cultural differences, insufficient/in- appropriate instruction, psychogenic factors), it is not the direct result of these conditions or influences. (Hammill, Leigh, McNutt, & Lar- sen, 1981, p. 336) This definition has been evaluated positively

compared to others (e.g., Interagency Commit- tee on Learning Disabilities, 1987; U.S.O.E., 1977; e.g., see Hammill, 1990; Silver, 1988). However, it is not an operational definition, be- cause it does not specify the operations or pro- cedures by which the construct of learning dis- abilities can be recognized and measured. For example, it is unlikely that current studies on learning disabilities would be published in refer- eed research journals if their subject sample de- scription relied solely on the NJCLD definition. Therefore, if we are to enhance our understand- ing of learning disabilities, serious consideration must be given to the selection of parameters that go into an operational definition. It is in this spirit that this special issue of the Learning Dis- ability Quarterly was developed.

In this opening discussion, I seek to distill some ideas that unify what otherwise might ap- pear to be a collection of unintegrated articles. The reader should remember, however, that each article is written from the authors' own research perspective. I deliberately solicited articles of di-

verse research perspectives to allow a number of issues to be considered. For example, in the first article Kavale, Forness, and Lorsbach discuss the limitations of operational definitions, whereas the article by Stanovich focuses on the irrelevancy of IQ. Likewise, Hynd, Marshall, and Gonzalez emphasize the relevance of studies originating from neuropsychology, Reynolds' ar- ticle targets psychometric models, while Bryan considers primarily social cognition. No doubt, to integrate these diverse perspectives will be no small feat. The purpose of this special issue, however, is not to show or seek unanimity among the contributors on how to operational- ize learning disabilities. Rather, the focus is on the commonality of conceptual issues that emerges in our attempts to operationalize learn- ing disabilities.

OPERATIONALIZING LEARNING DISABILITIES

Before reviewing each article in more detail, I will outline what I think are some fundamental points when one attempts to operationalize the term learning disabilities (LD). Three points are considered: selection of indicators, function of indicators, and parsimony. Selection of Indicators

The ultimate goal behind operationalizing the term learning disabilities is to enhance our abil- ity to replicate and generalize research findings to other samples with similar characteristics. Therefore, an obvious step in this process is for the researcher to specify the parameters or indi- cators used to determine a learning disability. That is, for each person with learning disabilities studied, a number is assigned that represents whether an indicator is present or absent, or

H. LEE SWANSON, Ph.D., Editor of the Learning Disability Quarterly, is Professor, School of Education, University of California- Riverside.

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"how much" of the indicator the person pos- sesses. Because learning disabilities cannot al- ways be defined directly (you might not know one when you see one), children with learning disabilities are usually separated from a general population on an array of indicators (see Hall & Humphreys, 1982; Wong, 1985; for a discus- sion on this issue). Traditional indicators for sam- ple selection include descriptive statistics from standardized intelligence, achievement and pro- cess measures, as well as the sample's age, grade level, gender, ethnicity, length of time in special education, and socioeconomic status (however, see Keogh, 1986b). Additional indica- tors are sometimes given to the study's setting and methodological characteristics.

These indicators must be selected with care. For example, merely reporting means and stan- dard deviations from standardized tests does not allow easy replication due to the difficulty of gathering another sample with the same average characteristics. Instead, to enhance replication, researchers must provide specific details on how the subjects were selected and what types of sub- jects were excluded. If control subjects are used, they also need to be detailed in the same specific manner.

For example, problems may emerge when cut- off scores on certain measures are used in the sample selection process (e.g., Fletcher, Espy, Francis, Davidson, Rourke, & Shaywitz, 1989). Although cut-off scores refine sample character- istics, they may introduce other constructs than the one intended by the researcher in framing the hypotheses. A cut-off score below the 25th percentile on a reading test, for example, may indicate an underlying construct of poor and/or nonsystematic instruction, rather than an inher- ent disability in mental processing (a fundamen- tal assumption of the learning disability construct; e.g., see Stanovich, 1986a, 1986b; Swanson, 1988). Thus, it is important to remember that indicators of learning disabilities may not be as exact as desired. Their selection involves both in- telligent decision making and construct valida- tion. However, this decision-making process is muddled by two factors: variations in sample se- lection and strategies for isolating processes.

Variations in parameter selection. A ca- sual review of the literature suggests the exis- tence of a wide array of parameters in opera- tionalizing the term learning disabilities (see

Keogh, 1983, 1988, 1990, for a review). For example, some students classified as learning disabled do not monitor their learning well (Borkowski, Estrada, Milstead, & Hale, 1989; Wong, 1991), cannot generate phonological codes effectively when processing visual infor- mation (Siegel & Ryan, 1988, 1989a, 1989b; Shankweiler & Crain, 1986), demonstrate poor metacognitive skills (Palincsar & Brown, 1987; Paris & Oka, 1989), and cannot negotiate social situations well (see Bryan, for a review, 1991).

Thus, depending on one's research interest, one might operationalize a student with learning disabilities as being unable (a) to think logically or symbolically, (b) to access a language system adequately, (b) to exhibit adaptive social behav- iors, and so on. This wide variation in the selec- tion of indicators makes it difficult to integrate findings, as well as to establish a common core of variables in sample selection (Frankenberger & Harper, 1987; Keogh, 1983, 1987; Shep- ard, Smith, & Vojir, 1983).

At this point, there appears to be little con- sensus in the field of learning disabilities on the directions one should go in operationalizing learning disabilities. This lack of direction is best captured by reviewing Alice's dilemma in Won- derland: "'Would you tell, me please, which way I ought to go from here?' said the Cat. 'I don't much care where-'said Alice. 'Then it doesn't matter which way you go,' said the Cat. 'So long as I get somewhere,' Alice added as an ex- planation. 'Oh, you're sure to do that' said the Cat, 'If you walk long enough"' (Carroll, 1916, p. 60).

Isolating operations. Given the diversity in possible directions for operationalizing learning disabilities, a strategy is needed for identifying a common set of indicators. One obvious strategy would be to combine several relevant dimen- sions of learning disabled children's adaptive and nonadaptive behavior (for example, classroom functioning) into an overall index or set of marker variables. Such an index would draw upon replicated findings across an array of re- search designs and measures. Although such a checklist or set of marker variables would be un- wieldy due to the number of items selected, in principle, at least, it might provide a common device for researchers to use in separating chil- dren with and without learning disabilities.

Of course, this ideal tool is unattainable since

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many of the relevant dimensions of learning dis- abled children's functioning, such as poor strat- egy use (e.g., Palincsar, Brown, & Campione, 1991), metacognitive deficiencies (e.g., Wong, 1991), or phonological awareness (e.g., Shank- weiler & Crain, 1986), are not standardized or even identified. Further, the learning disabled child's poor adapting characteristics would have to include not only measures of vocabulary, so- cial judgment, and general information, but also

flexibility of thinking, responsiveness to system- atic instruction, generalization of skills to various tasks, compensatory skills used within and out- side the classroom, and so on. These latter char- acteristics exhibit themselves only in unique situ- ations and others cannot be evaluated except by observing this child over an extended period. Thus, again, the researcher is left seemingly with unlimited possibilities in terms of operational definition. The selection process is further exac- erbated because of the lack of an accepted the- ory within the field (e.g., Swanson, 1988, also see commentaries), as well as political policies that ignore scientific data in the assessment of such children (e.g., see Adelman & Taylor, 1991; Chalfant, 1989; Keogh, 1986a, for re- view).

A more realistic strategy involves placing some constraints on these parameters by focusing on isolated operations, thereby operationalizing a learning disability in terms of a narrowly re- stricted range of operations. One example of an operational definition is outlined in an excellent chapter by Morrison and Siegel (1991) in which learning disabled children are defined as those who

(1) have IQ scores equal to or above 80 and (2) have one or more of the following: (a) WRAT (Wide Range Achievement Test) read- ing subtest scores equal to or below the 25th percentile, (b) WRAT arithmetic subtest score equal to or below the 25th percentile and WRAT reading scores equal to or above the mean on the Parent and or Teacher Question- naire. (Conners Parent and Teacher Rating Scales; see Goyette, Conners, & Ulrich, 1978, p. 91) This definition captures three high-incidence

disorders within learning disabilities: reading (word recognition), arithmetic (computation, written work), and attention. Consistent with the notion that a learning disability is intrinsic to the

child, each of these disorders is shown to dem- onstrate neurological and cognitive processing profiles (e.g., Fletcher, 1985). No doubt, such a definition presents a number of positive (e.g., easy identification for a broad constituency of re- searchers) and negative (e.g., construct validity, conceptual integrity) aspects. Of course, the ma- jor advantage in selecting this range of behaviors is that researchers utilize a common set of mea- sures that, in turn, enhance our chances of repli- cation.

Less restrictive definitions would attempt to capture operations that match some basic pre- mises in the field, most likely the following three assumptions: (a) learning difficulties are not due to inadequate opportunity to learn, general intel- ligence, or significant physical or emotional dis- orders, but to basic disorders in psychological processes; (b) these processing deficits are a re- flection of neurological, constitutional, and/or biological factors; and (c) there is a deficit that depresses only a limited aspect of contextually appropriate behavior.

Thus, when one attempts operationally to de- fine a phenomenon such as learning disabilities, an effort is made to measure adequate opportu- nity to learn (documentation that optimal sys- tematic instruction has occurred, but deficits in isolated processes remain); independence of spe- cific processing difficulties from general aca- demic aptitude (independence of a processing problem from general IQ); the relationship be- tween neuropsychological inefficiencies and cog- nitive processing difficulties; and so on. Criteria for selection of learning disabled children might include cut-off points on intellectual, neuropsy- chological, dynamic, and information-processing measures. However, problems arise when one attempts to expand the number of operations into a definition. Some of these problems relate to the limited number of valid and reliable instru- ments available (e.g., Kavale & Mundschenk, 1991) and the weak link between neurological and cognitive indices (Orbzut & Boliek, 1991). Function of Indicators

The value of an operational definition rests on the purpose of a given study. Therefore, when evaluating the meaningfulness of an operational definition, one must ask: what is the function and/or relationship between the operational def- inition and the research question? A research question such as "what are the characteristics of

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school-identified learning disabled children in special classrooms" requires a different set of operational parameters than "what are the pro- cessing deficits of learning disabled children high or low in social skills?". Thus, the value of the operational definition is linked to how specific the research hypothesis is.

Consistent with this issue is the notion of hy- pothesis specificity. For example, a research hy- pothesis such as the following: "poor reading in learning disabled children reflects more isolated processing deficits than in those who are slow or

generally poor readers," creates ambivalence about what to include in the operational defini- tion. It is more precise to assert that "poor read- ing in children with learning disabilities is caused by phonological coding among such children who only have a specific deficit in word recogni- tion." The phrase "among children who have a specific deficit in word recognition" clearly de- pends on a particular characteristic of the learn- ing disabled sample-specific to a reading prob- lem. In other words, the presumed cause of learning disabled children's reading problems is phonological coding (or vice versa). The re- searcher predicts that if the sample matches the operational definition of a certain subgroup- those with specific reading problems, those with reading and other problems-a clear relationship can be observed between phonological coding and the group with specific reading problems. Reading problems are not universally caused by phonological coding, according to the more pre- cise hypothesis, but only a segment of the par- ticular learning disabled population. These func- tions must be represented in the operational definition, the research question, as well as in the design of the study.

In sum, listing subject characteristics alone does not give substance to the operational defi- nition of learning disabilities. The researcher se- lects the observable indicators that best match the theoretical definition of learning disabilities. As a general rule, the more specific the sample, and the more specific the research question, the more detailed description is needed to define the subject sample. Parsimony

As a general principle, one may argue that the best operational definition of learning disabilities is one that has been consistently refined across several studies. According to the law of parsi-

mony, such a refinement process isolates rele- vant parameters while deleting irrelevant ones. As part of this process, one strategy is to deter- mine how much the parameters in the opera- tional definition influence the findings of the study. When this question is answered ade- quately, substantial progress can be made in identifying only relevant parameters for inclusion in operational definitions. For example, if IQ variations within a certain range of scores have little effect on the outcome of the study, such scores may be judged as irrelevant to the opera- tional definition of learning disabilities.

Some comment should be made on method- ological strategies that attempt to isolate rele- vant/irrelevant variables. At least three options are available: First, researchers can a priori de- fine their sample so that only subjects with per- formance patterns on certain variables are in- cluded. According to the above discussion, however, there is some question whether all or some of the subjects' characteristics are relevant to the research question. For example, if sub- jects are selected because they are white, male, have high SES, and have obtained IQ scores above 90, reading recognition scores below 25%, and math scores above the 35%, and if the researcher has a hypothesis about reading, is the issue of gender, ethnicity, and so on, rele- vant to the operational definition? Future studies may require that the researcher provide a ratio- nale for including descriptors based on their rele- vance to the learning disabled definition.

Second, the researcher can operationally de- fine and measure an isolated variable of interest (in this case, reading) from a more broadly de- fined list of parameters on a sample of learning disabled subjects. For example, the researcher can subgroup the sample into two or more groups on a particular task (e.g., task related to phonological awareness) and examine the effects of various processing tasks in each group.

A third method involves controlling relevant and/or irrelevant variables through research de- sign (e.g., reading-level matched design) or statis- tics (e.g., analysis of covariance with the influ- ence of IQ, reading comprehension, etc., par- tialled out).

Let us briefly consider research on the rele- vance of variables related to three assumptions: specific learning problems, performance discrep- ancy, and exclusion (for a comprehensive re-

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view, see Morrison & Siegel, 1991; Fletcher & Morris, 1986).

Specificity. Specificity refers to a learning problem that is confined to a limited number of academic or cognitive domains. The notion of specificity is tied closely to the way one classifies or subgroups performance. That is, children are classified and defined in terms of isolated pro- cessing, neurological, and/or academic deficien- cies. Example classifications have included the Wide Range Achievement Test (e.g., Fletcher, 1985; Rourke, 1982; Siegel & Linder, 1984), processing skills (Boder, 1973; Lyon, 1985a, 1985b), developmental processes (Morris, Blash- field, & Satz, 1988), speed/accuracy (Lovett, Barron, & Ransby, 1988), neuropsychological profiles (Rourke, 1982; Rourke & Fisk, 1988), and so on. Learning disabled children are op- erationalized in terms of problems in specific processes (e.g., phonological coding) and/or academic areas (such as reading) and further contrasted with children who have problems in other domains (e.g., mathematics), and/or chil- dren of equal achievement, ability, and/or chron- ological age. These approaches tend to stay away from rather generalized definitions of learning disabilities (e.g., NJCLD), focusing in- stead on smaller, more clearly defined subtypes. Although, conceptually, the notion of specificity is critical to operational definitions, endeavors along these lines have been criticized, primarily in three areas.

First, it has not been established that isolating children on a particular domain separates them from other children who also experience difficul- ties in those domains. For example, Siegel (1989) and Siegel, Levey, and Ferris (1985) found few differences in performance between dyslexic and poor readers on reading, language, spelling, and memory measures.

Second, the literature is unclear on whether operationally defined subgroups of learning dis- abled children respond differently to intervention (e.g., see Lyon, 1985a, for a review). Thus, the social validity of operational definitions can be questioned. For example, Stanovich (1986a) stated that there are no data to suggest that the discrepancy-defined dyslexic reader responds dif- ferently to various educational treatments than do ordinary poor readers. A possible exception to this finding is the work by Lovett et al. (1990), in which operationally defined sub-

groups who fail at reading at different develop- mental stages responded differently to interven- tion.

Finally, operational definitions are more driven by enhancing measurement procedures, via test- ing and classification procedures, than by an- choring definitions to a theoretical framework. Kavale and Mundschenk (1990) found that most measures commonly used in assessment batter- ies reflect a form of psychometric engineering that obscures the poor conceptual basis of the test. That is, the measures used for definitional purposes obscure whether the specific deficit identified is of adequate construct validity.

Discrepancy between IQ and achieve- ment. A number of operational definitions have attempted to establish that a learning disabled child's achievement is at a level that would not be expected based upon general ability. Tradi- tionally, identification of learning disabilities has relied primarily on uncovering a discrepancy be- tween expected achievement and intellectual ability.

One means of operationalizing discrepancies between potential and actual performance is to compare the scores of children with learning dis- abilities on different standardized tests. These discrepancies are quantified using (a) informal judgments; (b) grade-level expectancies and the degree to which a child deviates from grade-level expectancy; (c) mathematical formulas that em- phasize current achievement, IQ, or mental age; (d) standard score discrepancies; and/or (e) re- gression formulas that account for the effects of scores regressing toward the mean. The reliance on standardized tests to determine performance discrepancies is based on the assumption that la- tent sources of individual differences are related to mathematically derived constructs (i.e., fac- tors). Although interpretations of mathematically derived constructs are unequivocal (Carroll, 1983), the goal of such procedures is to isolate global constellations of the strengths and weak- nesses in the functioning of students with learn- ing disabilities. In a practical sense, it is assumed that standardized tests assess individual differ- ences along some continuum and that test items reflect an educationally relevant construct; other- wise, the tests would be of little interest or value as a means of determining discrepancies in the performance of students with learning disabili- ties. Critical to the assumption of a discrepancy

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is the notion of independence. That is, a learn- ing disabled child's global aptitude would not be adequately predicted from the deficit area (e.g., reading is weakly correlated with IQ), whereas the normally achieving counterpart would repre- sent a different correlational pattern (achieve- ment scores coincide with IQ).

Although the notion of discrepancy makes conceptual sense, it is probably the most con- tentious issue related to attempting to opera- tionally define a learning disability. The issues raised in several reviews (e.g., Kavale, 1987; Lyon, 1987; Reynolds, 1985; Shepard, 1983; Siegel, 1988b, 1989, 1990; Stanovich, 1986a, 1986b, 1989) may be summarized as follows:

1. IQ tests do not measure potential; there- fore, they should be excluded from discrepancy formulas. That is, IQ tests vary in the skills mea- sured (covarying abilities) and, therefore, do not constitute adequate representation of a unitary construct such as potential.

2. The intercorrelational patterns between IQ and achievement measures are not distinct be- tween ability groups.

3. IQ measures, in many cases, are not based on a learning model or theoretical framework.

4. Few cognitive differences exist between children with and children without discrepancies.

5. Discrepancies exist across a number of handicapped and nonhandicapped groups.

6. Discrepancy notions have been questioned on statistical grounds (this concern will be re- viewed in the article by Reynolds).

Concern has been voiced about analyzing per- formance discrepancies strictly based on psycho- metric measures. For example, although the psy- chometric instruments predict fairly well the stability of performance discrepancies (McKin- ney & Speece, 1986), it may be difficult to de- fine the mental processes necessary for effective learning, to identify subprocesses underlying aca- demic tasks, as well as global processes required for school learning, and to provide a link be- tween learning theories and educational practice (e.g., Wagner & Sternberg, 1984).

One promising framework for separating spe- cific processing deficits from general intelligence focuses on modularity, that is, psychological pro- cesses that act independently of one another (Fodor, 1983; Stanovich, 1990). Tentative sup- port for the concept of modularity has been found when processes that are most directly re-

lated to general intelligence (e.g., metacognition) are weakly correlated with lower level processes in a particular academic domain. In fact, some interesting results suggest that isolated reading processes, such as phonological coding, are in- dependent of intelligence (e.g., Siegel, 1990). Thus, to operationalize a construct such as mod- ularity, one would have to show that compo- nents related to intelligence (e.g., executive pro- cessing, prediction, self-monitoring) do not affect certain low-order processes during an ongoing cognitive activity. For an example, one would have to demonstrate that a high-level reading strategy, such as word or content predictability, remains independent of phonological access. As an illustration in the domain of reading, it has been suggested that high-level comprehension of discourse, such as the predictability of events (e.g., words), does not influence lexical access (see Balotta, Polatsek, & Rayner, 1985, for a re- view). It seems unlikely, however, that one would be able to show that a person's knowledge base and/or reasoning ability remains completely in- dependent of his or her ability to read.

Exclusion. Very seldom do research studies on learning disabilities report that concomitant disabilities exist. Instead, a clear effort is made to distinguish learning disabilities from other gen- eral handicapping conditions, such as mental re- tardation and visual and hearing impairments. Further, it is typically specified that bilingual, so- cioeconomic status, and conventional instruc- tional opportunity does not adequately account for the depressed scores. Thus, operational defi- nitions allow one to infer that the learning prob- lems experienced are intrinsic to the child.

Some investigators have challenged these as- sumptions (e.g., Braden, 1987; Kavale, 1980). For example, Rutter and Yule (1975) suggested that exclusionary definitions fail to specify the meaning of conventional instruction, sociocul- tural opportunity, average intelligence, and so on. Likewise, Taylor, Satz, and Friel (1979), in their comparison between children with dyslexia and children who had reading problems but did not meet exclusionary criteria (because of low IQ, low SES, etc.), found no group differences on several dimensions (e.g., severity of reading problems, neurological exams, parental reading levels, other achievement tests, reversal, and let- ter confusions). Further, Kavale (1980) argued that comparisons between learning disabled and

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culturally disadvantaged groups in terms of symptomatology suggest more similarities than differences. Hence, there is little evidence to in- dicate that operational definitions need to in- clude exclusionary criteria (Fletcher & Morris, 1986).

MAJOR DEFINITIONAL ISSUES After this overview of the issues, let us now re-

view some of the main points made by the con- tributing authors to this special issue. Testable and Meaningful Constructs

In the first article, Kavale, Forness, and Lors- bach suggest that defining learning disabilities has been one of the most contentious issues in the field. At the heart of the issue is the fact that definitions of learning disabilities do not possess experimentally testable constructs. Thus, what we think is learning disabilities is based upon so- cial consensus rather than meaning. Further, ef- forts towards narrowing the parameters of the definition may not capture the true essence of a disability. For example, restricting our focus to reading, speaking, writing, reasoning, or mathe- matical abilities does not capture the complexity of learning disabilities. To date, our definitions have focused on variability and not on a range of associated behaviors.

Kavale et al. also propose that we are limiting our understanding of learning disabilities when we focus on operational definitions. That is, pro- cesses used to define operations do not really de- fine. For example, any number of aptitude mea- sures (IQ) could be used to define expected achievement and an even greater number to de- fine actual achievement. Thus, our operations of learning disabilities are not precise because we have different concepts about what we do to measure aptitude, achievement, and so on. There are no rules by which to determine what are relevant or irrelevant operations.

The authors further argue that the poor state of learning disabilities theory prevents us from developing meaningful operational definitions. Thus, existing definitions, even those that in- clude notions about discrepancies, tell us little about what a learning disability is. As a result, Kavale et al. maintain that broadening the defini- tion to include social skills (see Bryan, this issue) is of little consequence when the theoretical mer- its of the definition have not been debated. In- stead, they recommend that we focus on opera-

tional interpretations of the best available knowledge. Choosing Conceptually Correct Measures

Stanovich also raises concerns about the learning disabilities definition, but argues that one concept - discrepancy - must be recon- ceptualized. Pointing out that at the heart of most learning disabilities definitions, especially as they apply to reading, lies assessment of a se- vere discrepancy between IQ and achievement, he maintains that the field has not adequately grappled with the issue of why IQ is used in dis- crepancy formulas. Specifically, Stanovich's ar- gument is that (a) IQ measures are not measures of potential; (b) it is difficult to differentiate read- ers of differing IQ; (c) variations in IQ tests cre- ate instability in subtypes; and (d) nonverbal IQ has little educational relevance. Although consid- erable research has been conducted on validat- ing the appropriateness of the discrepancy crite- rion (see Reynolds, this issue), such research suffers from an inability to separate readers with learning disabilities from poor readers. Further- more, Stanovich observes that the field of learn- ing disabilities is characterized by having plunged itself into areas of educational practice and diag- nosis without setting itself on a firm empirical foundation. As an alternative to IQ measures, he suggests that measures of listening comprehen- sion be considered. Linking Definitions to Neuropsychological Evidence

In the past, criticism has been leveled at neu- rologically based definitions of learning disabili- ties because of the yet-to-be-demonstrated neu- rological patterns claimed to match psy- chometric patterns of performance (Morris & Satz, in press; Satz & Fletcher, 1980; Satz & Morris, 1981). In addition, a discrepancy be- tween two federal definitions has brought further ambiguity into the neuropsychological criteria. That is, the PL 94-142 definition of learning dis- abilities removed the etiological role of neurolog- ical factors while emphasizing academics, whereas the NJCLD definition proposed a broader view of learning disabilities, stressing neurologically based causative factors. Currently, the importance of neuropsychological research in operationalizing learning disabilities is being reconsidered. Thus, sophistication of computer- ized (CT) scanning, magnetic resonance imaging (MRI), and positron emission tomography (PET)

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scanning, as well as genetic studies (e.g., Pen- nington & Smith, 1988) have generated a new interest in the biological basis of learning disabili- ties.

The article by Hynd, Marshall, and Gonzalez indirectly suggests that children who have diffi- culty organizing, coordinating and integrating, and/or synthesizing stimuli experience academic failure due to an underlying cerebral dysfunction. These authors' review of postmortem and neu- roimaging studies provides provocative evidence in support of a neurological conceptualization of learning disabilities. In general, these studies sug- gest that anomalies related to learning disabled children and adults appear as asymmetries favor- ing the left side of the brain, primarily the infe- rior frontal, temporal, and parietal regions - ar- eas that relate to linguistic functions. While indi- viduals with severe reading disability do not seem to demonstrate any obvious structural defect or lesion that would be a marker for learning dis- abilities (i.e., the brains of individuals with LD and normals may look the same), there is less asymmetry between the left and right sides or re- verse asymmetry of the brain for the disabled than for the nondisabled population. These devi- ations are more likely related to neuropsycholog- ical development than brain damage or lesions in the postnatal period. Hynd et al.'s analysis also suggests specific deviations in learning disabled children's brain asymmetry that separate them from ADD/H children, for example.

In sum, the results of Hynd et al.'s analysis point to support for the notion that learning dis- abled children suffer neurological inefficiencies. However, because of the heterogeneity of the population, one cannot conclude that learning disabilities is strictly due to central nervous sys- tem dysfunction. Hynd et al.'s analysis is consis- tent, however, with the notion that severe learn- ing disabilities is related to neurological factors. Measuring a Discrepancy

From a psychometric perspective, the critical question for the field of learning disabilities has been a severe discrepancy between a student's current level of academic attainment and the mean level of all other children of the same age, ability, or IQ score. In this issue, Reynolds sug- gests that it is possible to improve the objective identification of learning disabilities by emphasiz- ing the discrepancy between age, ability, and current academic psychological process.

The concept of a severe discrepancy remains key for two reasons: (a) it denotes a validated criterion compared to other criteria; and (b) it denotes specificity. Unfortunately, as the article by Reynolds indicates, the use of different mea- surement models has created ambiguities in the population served within and between several states (Frankenberger & Harper, 1987; Merrell & Shinn, 1990). Based on a review of formulas (favoring the regression formula) and issues re- lated to significant discrepancies, Reynolds con- cludes that the determination of a severe dis- crepancy does not create a sufficient condition for establishing a learning disability. Instead, one must demonstrate problems in basic information processing, possibly related to neuropsychologi- cal inefficiencies, as well as establish that unique or differentiated instruction has occurred. Social Cognition

The importance of social cognition in defining learning disabilities has been noted by the Inter- agency Committee on Learning Disabilities (1987), which suggested that children with LD manifest difficulties in social skills (see Forness & Kavale, 1991, for discussion). A recent chapter by Bryan (1991) provides a timely analysis of the extant literature on social cognition, specifi- cally in the areas of perspective taking, moral development, and social problem solving. In her present article, however, Bryan argues that crit- ics of learning disabilities research, such as those who question whether the sample selection is operationally defined, are placing undue restric- tions on research - restrictions that, in turn, threaten progress in the field. Citing examples of research that has challenged current opera- tional notions, and, in turn, has caused a refor- mulation in our thinking of learning disabilities, Bryan maintains that undue constraints on our definition of learning disabilities have a decided affect on the directions taken by researchers

Although criticism of the field has overly fo- cused on definition, she suggests that a shift is occurring, away from definition to the issue of research. Thus, sample selection becomes a sec- ondary concern, while greater emphasis is placed on the commonality of findings. Accord- ing to Bryan, results across variously defined samples have been fairly consistent and provide a common thread that mitigates issues of defini- tion and methodology. Further, she notes some research bias against selecting school-identified

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learning disabled students, pointing out that this group of students keeps emerging, in spite of ef- forts to make sample selection more strict. Ac- cording to Bryan, loosely defined samples are worthy of investigation, if for no other reason than to establish social validity. She further ar- gues that if constraints are to be placed on the information collected on children defined as learning disabled, then self-concept information should be collected. Her point is that careful sub- ject selection should be based upon previous work, not on setting undue standards in sample selection.

CONCLUSIONS AND NEW DIRECTIONS In general, based on the authors reviewed

here, it can be stated that (a) our operational def- initions must have conceptual meaning (Kavale, Stanovich); (b) we must question the measures selected to establish a discrepancy (Stanovich, Reynolds); (c) we must not be restrictive in our definitions, but look for patterns of continuity in research results (Kavale et al., Bryan); and (d) we need to bolster our notion about the intrinsic dif- ficulties in processing information (Hynd et al.).

As professionals in the field, we have some se- rious thinking to do if we are to capture the complexity of a learning disability. Specifically, the learning disabilities field must consider and scrutinize a number of operational definitions. The field is too new to isolate and accept a com- mon set of measures that reflect a narrow range of operations. For example, serious considera- tion must be given to alternative measures of po- tential (such as suggested by Stanovich) and achievement. On the other hand, operational definitions must be derived from an accumulating knowledge base. Thus, the field should not give serious consideration to operational definitions that deviate too far from some of the critical as- sumptions mentioned earlier.

Other points could be considered in attempts to operationalize learning disabilities. Thus, this special issue is far from a final commentary on the operationalization of learning disabilities. Suggestions should be made for future research direction. I will attempt to make two. My sugges- tions are not based on a systematic analysis of operational definitions, but originate in the per- spective of an editor for a journal that publishes learning disabilities research. Therefore, my sug- gestions are biased.

First, I believe it is necessary for us to re- work/reformulate our conceptual definitions within the context of learning theory. The au- thors in this special issue agree that we need to reconceptualize what we want our operational definition to include, articulate the parameters of the definitions, and ensure that our definition emanates from a sound theoretical framework that captures the processes of learning as well as the context in which learning occurs. Thus, defi- nitions in published research reports must articu- late the framework within which they are oper- ating. I would suggest that this endeavor entails reformulating some common assumptions that have a historical reference (such as those repre- sented in the NJCLD definition). After this con- ceptual reworking, operationalized definitions and measures could be established. Such mea- sures, in turn, would require a validity and relia- bility analysis.

I will illustrate this first phase by taking some liberty in synthesizing the research literature on learning disabilities from an information-process- ing perspective. While other perspectives can be considered, this is the most familiar to me. It ap- pears to me that most studies published in psy- chological/educational and neuropsychological journals define, at least in part, a person with learning disability as an individual with least av- erage general academic aptitude (consistent with Siegel and Stanovich's work, IQ test is not obli- gatory) who unexpectedly has difficulty per- forming certain cognitive processes and/or op- erations. The person's performance patterns on general aptitude measures reflect a factor struc- ture comparable to that of nondisabled counter- parts on tests that load high on "g".

Problems in effectively utilizing certain cogni- tive processes, however, are reflected on tasks that make heavy demands on specific low-order processes (e.g., nonword reading tasks that rely on phonological codes) and/or higher order pro- cesses (e.g., problem-solving tasks that rely on metacognition) and/or processes that are sensi- tive to academic domains such as reading, math- ematics and writing. The discrepancy between the person's average global information-process- ing ability and his or her impairment on isolated processes is assumed to be due to a cognitive/ neurological constraint or inefficiency. As men- tioned, this constraint or inefficiency manifests itself in specific lower order processing (e.g.,

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awareness and monitoring of attentional re- sources) and/or processes that facilitate the in- teraction between or coordination of lower and higher order processes.

I admit that I am on shaky ground because the literature is unclear about how specific high- and low-order processes interact or remain function- ally independent while a learning disabled stu- dent performs on an academic task (e.g., see Stanovich, 1990; Swanson, 1989). But I have couched my conception of learning disabilities within an information-processing framework. Research in this vein would have to operational- ize a possible model to understand the depen- dence or independence among processes. This may be done by considering how learning dis- abled children's knowledge about various situa- tions or contexts (such as a reading context) in- fluences their cognitive processing. In designing my study, I would also have to provide a ratio- nale for the instrumentation by which learning disabilities is defined.

Second, after my notions about learning dis- abilities have been matched to a conceptual framework, future variations in operationaliza- tion would need to follow a research agenda. A proposed agenda for the new decade may in- clude the following: 1. Measures must be analyzed in terms of con-

struct validity. The researcher is encouraged to provide multiple measures of potential and specific disability to ensure generality of the construct across tasks. Further, it is important that the measures come from a well-devel- oped theory of learning.

2. Rigorous experimental and quasi-experimen- tal designs should be used to compare learn- ing disabled children with their counterparts. Further, multiple experiments will need to be published in order to enhance replication.

3. The learning disabilities construct needs to be tested in various contexts (within and outside the classroom).

4. Qualitative research designs need to be used in tandem with quantitative approaches. In conducting such research, it is vital to incor- porate conventional credible procedures (e.g., a complete rejection of reductionistic work would be inappropriate).

5. Information should be provided in the opera- tional definition to demonstrate stability and/ or durability of the construct. For example, if

learning disabilities is due to an inability to benefit from the best instructional approach, some documentation must be gathered to demonstrate that the child has been exposed to such instruction. For example, it would not make sense to classify a child as having a phonological coding deficit if systematic in- struction could easily modify such a problem. Thus, systematic effects of previous class- room instruction on learning must be mea- sured.

6. The possibility that children defined differ- ently by various operational definitions re- spond differently to instruction must be fully explored.

7. Future research studies must tie cognitive and academic performance with neuropsychologi- cal data. If the field is to assume that LD problems are intrinsic to the child, further de- velopment and use of neuropsychological in- dices is necessary. In addition, some of these indices must be available for assessment in the public school context (in contrast to MRI and PET scanning).

In summary, the theme that underlies most of the articles in this issue is that operational defini- tions of learning disabilities must be directed by a strategy that makes a serious attempt to cap- ture meaningful constructs. Thus, an adequate operational definition of learning disabilities not only focuses on measurement, replication of sample, and meeting critical assumptions, it also takes into consideration its meaningfulness. Meaning is here defined in the context of the- ory, research question and design, as well as the construct validity of measures that capture the child's environmental and behavioral interac- tions, developmental structures, biological con- straints, and cognitive processes.

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