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.
- 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.
- 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.
- 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.
- 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
- 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.
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.
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