Dyslexia

Dyslexia is a learning disability that manifests itself primarily as a difficulty with reading and spelling. It is separate and distinct from reading difficulties resulting from other causes, such as a non - neurological deficiency with vision or hearing, or from poor or inadequate reading instruction. [1] This suggests that dyslexia results from differences in how the brain processes written and spoken language.
There are many definitions of dyslexia but no consensus. Some definitions are purely descriptive, while others embody causal theories. It appears that ‘dyslexia’ is not one thing but many, in so far as it serves as a conceptual clearing - house for a number of reading skills deficits and difficulties, with a number of causes.

The majority of currently available dyslexia research relates to the alphabetic writing system, and especially languages of European origin. However more research is becoming available regarding dyslexia in speakers of Hebrew and Chinese. This article provides a broader and more universal perspective of dyslexia.

Castles and Coltheart, 1993, described phonological and surface types of developmental dyslexia by analogy to classical subtypes of acquired dyslexia ( alexia ) which are classified according to the rate of errors in reading non - words. [3] However the distinction between surface and phonlogical dyslexia has not replaced the old empirical terminology of dysphonetic versus dyseidetic types of dyslexia ( Boder 1973 ). The surface / phonological distinction is only descriptive, and devoid of any aetiological assumption as to the underlying brain mechanisms, in contrast the dysphonetic / dyseidetic distinction refers to two different mechanisms one relates to a speech discrimination deficit, and the other to a visual preception impairment. ( Most people with dyslexia who have Boder ' s Dysiedetic type, have attentional and spatial difficulties which interfere with the reading acquisition process.

Although dyslexia is thought to be the result of a neurological difference, it is not an intellectual disability. Dyslexia is diagnosed in people of all levels of intelligence.