Language versus learning disorder: part 2

 

In the previous post, we saw how language disorder is defined in the DSM-5, and discussed the differential diagnosis between language disorder and learning disorder in the DSM-5. We will now discuss language disorder versus learning disorder according to Flanagan’s definition.

First, let us recall Flanagan’s definition of learning disability/disorder:

·       Low performance in reading/writing/arithmetic: scores at least one standard deviation below the age-based mean on tests that directly assess reading/writing/arithmetic.

·       One or more low cognitive abilities: the scores on most of the tests assessing that ability should be at least one standard deviation below the age-based mean.

·       The low cognitive ability or abilities must be capable of explaining the low performance in reading/writing/arithmetic. For example, low phonological awareness — poor auditory processing — can explain low accuracy in reading single words and pseudowords.

·       Most cognitive abilities should be intact. In other words, most of the test scores assessing each such abilities should be above 85, where the mean is 100 and the standard deviation is 15.

·       Finally, exclusionary factors such as sensory impairment, intellectual disability / intellectual developmental disorder, emotional or social disturbance, cultural differences, or inappropriate instruction cannot provide a better explanation for the low performance in reading/writing/arithmetic.

All five of these criteria — as well as interference with daily functioning, which goes without saying — must be met for a child to be defined as having a learning disability according to Flanagan’s definition.

 

Flanagan’s definition is usually applied together with the CHC model. Since we are discussing language disorder, we will now look at the CHC definition of crystallized knowledge.

Crystallized knowledge is the ability to understand and communicate culturally valued knowledge. Crystallized knowledge includes the breadth and depth of declarative and procedural knowledge and skills, such as language, words, and general knowledge, that have developed through experience, learning, and acculturation — that is, cultural adaptation (Schneider & McGrew, 2018).

Here are the definitions of the narrow abilities of crystallized knowledge (Schneider & McGrew, 2018):

1. Language development: the ability to understand and communicate through language. General comprehension of spoken language at the level of words, phrases, and sentences. Language development includes spoken and written language, both receptive language — comprehension — and expressive language — expression.
2. Lexical knowledge: knowledge of word definitions and the concepts underlying them. Vocabulary knowledge.
3. General knowledge: the breadth and depth of knowledge considered necessary and valued in a given culture.
4. Listening ability: the ability to understand speech, ranging from single words to long and complex verbal utterances. In other words, the ability to understand receptive spoken language.
5. Communication ability: the ability to use words in order to communicate effectively.
6. Grammatical sensitivity: awareness of the formal rules of grammar and the morphology of spoken words.

The language difficulties required under the DSM-5 definition of language disorder are persistent difficulties in the acquisition and use of language across modalities — for example, spoken language, written language, sign language, or another form — due to deficits in comprehension or production, including reduced vocabulary — word knowledge and word use — limited sentence structure — difficulty forming proper sentences according to the rules of grammar and morphology — and impairments in discourse — difficulty using vocabulary and sentences to explain or describe a topic or a series of events, or difficulty holding a conversation.

It is easy to see that the narrow abilities of crystallized knowledge encompass all the language difficulties included in the DSM-5 definition of language disorder.

When we are dealing with a school-age child who has low performance in reading/writing/arithmetic and low crystallized knowledge, and we see that the low crystallized knowledge impairs the child’s reading/writing/arithmetic functions, that child will have a learning disability according to Flanagan’s definition, provided that most of the child’s abilities are intact and that exclusionary factors do not better explain the child’s difficulties in reading/writing/arithmetic.

In such a case, the diagnosis of language disorder is actually included within the diagnosis of learning disability according to Flanagan, and will be reflected in low crystallized knowledge. I will emphasize two points: First, crystallized knowledge should be assessed comprehensively, using not only tests that assess vocabulary and general knowledge, but also tests that assess grammar and syntax, expression, and comprehension. Second, low performance / impairment in crystallized knowledge, which usually appears at an early stage of development, may cause not only difficulties in reading/writing/arithmetic, but also difficulties in spoken language.

McArthur et al. (2000) examined 110 ten-year-old children with reading disability and 102 ten-year-old children with language disorder. They found that 55% of the children with reading disability had impairments in spoken language, and that 51% of the children with language disorder had impairments in reading. Thus, the degree of overlap between the two disorders is in fact very large, raising questions about the differences between them in school-age children and older children.

There are three situations in which a child with low crystallized knowledge will not have a learning disability according to Flanagan’s definition. The first situation is that of a young child with low crystallized knowledge who has not yet formally learned reading/writing/arithmetic. Such a child cannot have low performance in reading/writing/arithmetic relative to what is expected for his or her age, and therefore, will not be defined as having a learning disability, but rather as coping with a language disorder / disability in crystallized knowledge.

The second situation is that of a child whose low crystallized knowledge does not impair reading/writing/arithmetic at all. It is difficult to think of such a situation, but theoretically it is possible. Flanagan’s definition requires us to verify that the low cognitive ability we found indeed explains the child’s low performance in the areas of achievement — reading/writing/arithmetic. If crystallized knowledge is the child’s only low ability, and we are not convinced that this ability causes the child’s specific difficulties in reading/writing/arithmetic, then we cannot determine that the child has a learning disability according to Flanagan’s definition. We will, however, be able to determine that the child is coping with a language disorder — assuming, of course, that crystallized knowledge / language has been measured in a comprehensive and broad manner.

The third situation is one in which not only the child’s crystallized knowledge is low, but most of the child’s cognitive abilities are low. In this situation as well, the child will not have a learning disability, but will be a slow learner (or will have general learning difficulty). Language disability will be only one of several cognitive disabilities that such a child has.

This is still not the whole story. Sometimes, additional cognitive difficulties underlie language difficulties. For example, Leonard et al. (2007) found that working memory and processing speed explain 62% of the variance in language-test scores among adolescents with language disorder. In other words, a good assessment of these children should include not only an assessment of language, but also an assessment of other cognitive abilities. The DSM-5 definitions of language disorder and learning disorder do not require an assessment of cognitive abilities, and may therefore miss important factors contributing to the child’s difficulties.

To summarize the two posts on this subject: is language disorder an exclusionary factor for learning disorder in a school-age child with difficulties in reading/writing/arithmetic?

If one works according to the DSM-5, language disorder may be an exclusionary factor for learning disorder if it is the primary cause of the child’s difficulties in reading/writing/arithmetic.

If one works according to Flanagan’s definitions, low crystallized knowledge, when assessed comprehensively, is parallel and identical to the language difficulties required for the definition of language disorder. Thus, a school-age child with difficulties in reading/writing/arithmetic, whose low crystallized knowledge can explain his or her academic difficulty, and whose academic difficulty is not better explained by exclusionary factors, has a learning disability — originating in a disability in crystallized knowledge/language. Under this conceptualization, language disorder is not an exclusionary factor for learning disability/disorder, but is included within the definition of learning disability/disorder.

 

Leonard, L. B., Weismer, S. E., Miller, C. A., Francis, D. J., Tomblin, J. B., & Kail, R. V. (2007). Speed of processing, working memory, and language impairment in children. Journal of Speech, Language, and Hearing Research, 50(2), 408–428.

McArthur, G. M., Hogben, J. H., Edwards, V. T., Heath, S. M., & Mengler, E. D. (2000). On the “specifics” of specific reading disability and specific language impairment. The Journal of Child Psychology and Psychiatry and Allied Disciplines, 41(7), 869–874.

Schneider, W. J., & McGrew, K. S. (2018). The Cattell-Horn-Carroll theory of cognitive abilities. In Contemporary Intellectual Assessment: Theories, Tests, and Issues, 733, 163.