Editorial: Subtypes of LD

Could identification of sub-groups help guide instructional programming?

Have you been hearing a lot about subtypes of learning disabilities lately? Perhaps it’s just that I’ve been especially alert to it, but it seems I’ve heard a lot of mentions about subtypes of learning disabilities in the last few weeks. (There’ve also been questions about subtypes of autism spectrum disorder!)

First, the idea of subtypes of LD is essentially a given. It has to do with the heterogeneity of LD. Because LD is essentially an umbrella category for a diverse array of learning disabilities (note the plural), there are bound to be subgroups. Some students will have problems primarily with reading, some primarily with arithmetic and mathematics, some with writing, others with combinations of these. That makes for lots of subgroups right there. That is, one could start with dyslexia, dyscalculia, and dysgraphia!

Second, authorities studying attention, memory, perception and other processes they consider to be associated with learning disabilities have been on the hunt for subtypes based on those processes for as long as I have been reading the literature in LD. Early on, a lot of it was relatively seat-of-the-pants searches for patterns in scores on popular tests (“jagged profiles”), and these searches were often driven more by they theory of the searcher than by the evidence itself. However, research became much more sophisticated in the 1980s, when several folks (including Don McKinney and Reid Lyon) used modern research methods and sophisticated statistical analyses to identify subtypes of students with Learning Disabilities based on data rather than hunch. For example, Speece et al. (1985) identified seven different subtypes of students with learning lisabilities based on differences in their social behavior (independence, extroversion, task orientation, considerateness, dependence, introversion, distractibility, hostility), two of which were pretty similar to their normal peers. In many of these studies, subtypes that the researchers identified proved to be stable and valid, but they didn’t have much utility for guiding instruction. (For those who are interested in some of the subtyping research of the 1980s and more recently, I have appended a few references.)

And, that’s the third point. For subtyping research to be of substantive value, it has to help us improve services. It’s great if it helps people such as I “understand” LD better. I like learning about learning disabilities. But, the real place where the rubber meets the road is improving outcomes for individuals with learning disabilities. The measuring stick for the success of sub-typing research isn’t just that we can do it—I know we can do it—but that it provides guidance to better services, to better instruction, that it has diagnostic validity. 

There are diverse ways to search for subtypes of disabilities (and other phenomnena, as well). The statistical methods—whether a researcher is using “latent-trait analysis” or “cluster analysis” (to name two major methods)—boil down to measuring many individuals along important dimensions and then one can spot patterns among the various scores for some of the individuals that differ from patterns spotted for other individuals. An edited book by Feagans and colleagues (Feagens et al., 2012) provided scholarly chapters about both methods and results.

It turns out, so far at least, that the search for subtypes hasn’t gotten us any farther toward helping students learn any better than the basic powerful instructional methods that we should be applying anyway. We should start with ensuring that students, whether they have Learning Disabilities or not, experience the very best educational environments that we can muster, the kinds of environments that we know predict the best outcomes in the long run for the vast majority of students. If that sounds like great Tier 1 instruction, then you’re getting my drift. 

And in those super-duper settings, we should systematically monitor students’ academic and social performance on a regular basis; if we see some students who aren’t quite keeping pace with the kind of progress that predicts successful outcomes, we should quickly—no waiting!—start scheduling extra help for them: Make sure that they get the extra repetitions, more supports, supplemental materials, smaller groups, and such. And we should keep monitoring these students’ progress even more closely. 

And if the trajectory of progress, the trend line, does not start trending toward the success range, then the educators in charge should call together a team composed of the child’s parents or guardians and some highly skilled special educators and related-services folks and they should examine the child’s case and decide whether she needs special education and, if she does, what unique special education needs she has, how to meet those needs, how to know if those needs are being met, and so forth (i.e., determine eligibility and, if needed, develop an IEP).

When it gets down to it, once a student has been identified as eligible for special education because of Learning Disabilities, she’s a subtype of one. What do you think?

Note: I originally published an earlier version of this post 25 July 2011 on LDBlog.

Bibliography

Feagans, L., & Appelbaum, M. I. (1986). Validation of language subtypes in learning disabled children. Journal of Educational Psychology, 78,358-364. doi: 10.1037/0022-0663.78.5.358

Feagans, L. V., Short, E. J., Vernon-Feagans, L., & Meltzer, L. J. (Eds.). (2012). Subtypes of learning disabilities: Theoretical perspectives and research. Routledge.

Lyon, G. R., & Watson, B. (1981). Empirically derived subgroups of learning disabled readers: Diagnostic characteristics. Journal of Learning Disabilities, 14, 256-261.

McKinney, J. D., & Speece, D. L. (1986). Academic consequences and longitudinal stability of behavioral subtypes of learning disabled children. Journal of Educational Psychology, 78, 365-372. doi: 10.1037/0022-0663.78.5.369

O'Brien, B. A., Wolf, M., & Lovett, M. W. (2012). A taxometric investigation of developmental dyslexia subtypes. Dyslexia, 18(1), 16-39. https://doi.org/10.1002/dys.1431

Rourke, B. R., & Strang, J. D. (1983). Subtypes of reading and arithemtical disabilities: A neuropsychological analysis. In M. Rutter (Ed.), Developmental neuropsychiatry. New York: Guilford. 

Speece, D. L., McKinney, J. D., & Appelbaum, M. I. (1985). Classification and validation of behavioral subtypes of learning-disabled children. Journal of Educational Psychology, 77, 67-77. doi: 10.1037/0022-0663.77.1.67

Tamboer P., Vorst, H. C. M., & Oort, F. J. (2016). Five describing factors of dyslexia. Journal of Learning Disabilities, 49(5), 466-483. doi:10.1177/0022219414558123