Nonverbal learning disability – is it possible to define it in terms of CHC theory? Part one.

The interesting idea to write about this subject is Meir Buchner's.

A search for papers referring directly to this subject did not yield results, so I'll try to make my own conjectures.  Due to this post's length I divided it into two parts.

In this part we'll look at the symptoms of nonverbal learning disability (NVLD).

The definition of NVLD is in dispute.

Mammarella &  Cornoldi  reviewd 35 NVLD studies and derived five diagnostic criteria.  They stress that the criteria are preliminary, since NVLD was defined differently in each study.  There is a need for more research done with a consensual definition.

Here is Mammarella &  Cornoldi's paper:

Irene C. Mammarella & Cesare Cornoldi (2014) An analysis of the criteria

used to diagnose children with Nonverbal Learning Disability (NLD), Child Neuropsychology: A Journal on Normal and Abnormal Development in Childhood and Adolescence, 20:3, 255-280,   http://dx.doi.org/10.1080/09297049.2013.796920

Of these five criteria, the authors find the first criterion necessary.  At least two of the criteria 2-4 are required, and the fifth criterion is possible.

1. Low visuospatial ability with relatively good verbal ability.  A significant discrepancy between measures of verbal ability (in CHC terms, comprehension knowledge) and measures of perceptual or visuospatial ability (in CHC terms, visuospatial processing).  The authors suggest that the discrepancy should be at least one standard deviation.  A child does not meet this criterion if his verbal ability is significantly higher than average (say, above 115) and his visuospatial ability is average.  A child does not meet this criterion if his verbal ability is significantly lower than average (say, below 85) and his visuospatial ability is two or more standard deviations below average. 
2. Visuoconstructive and fine motor  impairments.  This ability is usually measured by reproduction of geometric figures.  We don't only look at the individual's aptitude for copying a figure, but how well planned and organized that figure is.  This ability is usually measured by tests like the BEERY and RCFT.   Performance is poor if it's one or more standard deviation below average.  The authors recommend using more than one test.  With two tests performance is poor if one of the test's scores is one and a half standard deviation or more below average. 
3. Poor math achievement at school along with relatively good reading decoding ability.   NLD children do not usually have trouble recalling arithmetical facts, but they make visuospatial errors in written calculations (i.e., confusing columns, carrying/borrowing errors) and write mirrored numbers.   Not all studies find poor performance in standardized mathematics tests.  The authors recommend basing the diagnosis on a discrepancy of at least one standard deviation between intact reading decoding and poor mathematics achievement.  They recommend looking for qualitative signs of math difficulties resulting from visuospatial difficulties. 
4. Poor spatial working memory.  The problem is, that I'm not sure the authors are distinguishing  between  spatial working memory and  spatial memory.  When writing about this criterion they sometimes write " spatial working memory" and sometimes "spatial memory".  Tests measuring  spatial working memory present the child with a series of spatial stimuli, on which he has to perform mental manipulations and respond immediately.  Tests measuring spatial memory present the child with spatial stimuli and measure his ability to retrieve them after a period of time (after four minutes or more), with no manipulation.  When I looked at the tests that were used in the studies measuring  spatial working memory, usually I couldn't tell what they were, because they are described vaguely as "spatial working memory tests" or "visuospatial organization problems".  Anyway, the authors recommend that the score on a test measuring spatial working memory should be lower than average by one standard deviation or more (when using one test) and one and a half standard deviation or more in one of two tests used
5. Social and emotional difficulties.   The authors list this as another criterion for identifying a subgroup of children with NVLD.  Difficulties understanding emotions and difficulties with social skills  should  be present at school and at home and should be assessed by a clinical interview and observation.  The authors suggest using questionnaires and clinical interviews with parents and teachers.

All of the above is from Mammarella &  Cornoldi's study.

Flanagan and her colleagues, in a paper about the WISC4 test,

Flanagan, D. P., Alfonso, V. C., Mascolo, J. T., & Hale, J. B. (2011). The Wechsler Intelligence Scale for Children–Fourth Edition in Neuropsychological Practice.‏

http://static1.squarespace.com/static/53f6762ae4b02e1724aa7c77/t/542e1ed1e4b0e285694d4a47/1412308689824/Flanagan_et_al_in_Davis_Handbook.pdf

write that children with NVLD have poor math performance and poor performance in the PRI (perceptual reasoning index) and the PSI (processing speed index).  The PRI consists of the tests matrix reasoning, Block Design and Picture Concepts.  The matrix reasoning test measures fluid ability (using visual stimuli).  It's possible that processing speed is poor because the tests measuring processing speed also use visual stimuli.

Flanagan  adds, that children with NVLD performed well on forward digit span and had poor performance on backward digit span.

Rourke suggested a definition for NVLD in 1995,  that was accepted by many researchers.  According to this definition, children with NVLD have high verbal ability, good verbal rote memory, phonological awareness, verbal fluency and good verbal classification ability.  These children have weak visuospatial skills, perceptual and motor skills and nonverbal problem solving skills.  They have difficulties with math but intact word reading skills.  Often they have social difficulties resulting from visuospatial difficulties, that affect their ability to read social and visual cues like gestures and facial expressions.   This definition is from this study:

Larsen, J. M. (2011). The impact of visual memory deficits on academic achievement in children and adolescents (Doctoral dissertation, The University of Utah).‏  http://content.lib.utah.edu/utils/getfile/collection/etd3/id/461/filename/589.pdf

To all this I'll add from personal experience, that children with NVLD sometimes have reading comprehension difficulties (understanding latent and implicit meanings in texts and content related to social and cultural norms), analyzing and synthesizing a whole into parts and parts into a whole  (not only with visual stimuli, but generally paying a lot of attention to details and having difficulty seeing the gestalt), handwriting difficulties, poor drawing and written expression, and trouble understanding intonation.

Is it possible to define NVLD in terms of CHC theory?  In the next post.