A definition of developmental dyscalculia, stressing the hereditary or congenital affection of the brain substrate of mathematical functions, is put forth. This disorder is clearly distinguished from other forms of disturbed mathematical abilities. A classification of developmental dyscalculia is then outlined, distinguishing the following forms: verbal, practognostic, lexical, graphical, ideognostical and operational developmental dyscalculia. Finally an investigation is presented of mathematical abilities and disabilities in eleven-year-old pupils from normal schools in Bratislava, Czechoslovakia. A number of tests measuring symbolic functions were applied to 66 suspected dyscalculics with normal IQs who had neurological examinations. The tests are characterized and the results briefly described; some examples of concrete pathological solutions to test items are given. This investigation suggests that nearly 6% of children of the so-called normal population can be justifiably expected to have symptoms of developmental dyscalculia as defined in this study.
An 11-year-old, Hebrew speaking boy of normal intelligence, referred to Alyn Hospital, and Schneider Children's Medical Center, Jerusalem, for evaluation of learning and attentional problems, was found to have a profound dyscalculia based on a proposed lack of "cardinal/ordinal skills acquisition device" (COSAD). Several male family members had dysgraphia, right-left disorientation, and dyslexia. At birth, the child was hypotonic, and motor development was delayed, walking independently at 2 and 1/2 years. Neurologic abnormalities included high-pitched voice, dysgraphia, right-left disorientation, finger agnosia, clumsiness in running and jumping, scoliosis, and fine motor incoordination. At 4 years, he developed grand mal seizures treated with carbamazepine, and at 7 years he received pemoline (Cylert) for ADD without hyperactivity. The pemoline benefited overall functioning. The use of linguistic, visual and verbal memory cues compensated for deficits in ordinal number use, but not for cardinal number skills, which remained limited. He could count small numbers, but could not do simple calculations, a skill requiring an innate experience of quantity, less amenable to language, visual-spatial, or logical mediation. Different theories of number development and mathematical skills are discussed in relation to mechanisms of dyscalculia and its management. (Ta'ir J, Brezner A, Ariel R. Profound developmental dyscalculia: evidence for a cardinal/ordinal skills acquisition device. Brain and Cognition November 1997;35:184-206). (Reprints: Judy Ta'ir, Alyn Hospital, PO Box 9117, Jerusalem 91090, Israel).
Learning disabilities (LD) need not be defined as such. It is satisfactory to explain what is meant by “learning“ and “disability.” Disability is conceived as a structural disturbance of a particular ability. In principle, LD is a psychological term dealing with many different kinds of psychological traits or processes, and their disturbances, respectively. LD is to be strictly distinguished from more educationally conceived “learning failures,” as well as from more medically/neurologically conceived “dysfunctions” of learning. The label LD cannot be used in clinical practice as a diagnosis, or in research as an independent variable. For both purposes, LD must be specified and/or operationally defined. If a definition of LD (or specific LD) is needed for professional communication, then a more sophisticated definition than those currently in use is needed as a starting point for further relevant discussion.
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