ence of sensory defect or overt organic damage, have an intractable learning problem in one or more of reading, spelling or maths, and who do not respond to normal teaching" (see Critchley and Critchley 1981). This definition however raises the new issues of "specific learning difficulties" (SPLD), "sensory defects", and "organic damage". The issues of sensory defects and organic defect will be dealt with later, as a means of determining how accurate this definition is.
             Know that a satisfactory definition has been established for dyslexia, we will progress onto examining the causes and contributors of this condition. As a way of simplifying this process the causes will be separated into several categories (genetic, perceptual, neurological and linguistic).
             The question of genetics has long been linked to dyslexia, or "congenital word blindness" as Hinshelwood, Morgan and Kerr named it in 1900 after studying the incidences of intelligent people who could not read, and who were related, founding the idea that dyslexia is partly geneticall y determined (see Huston, 1987). This initial research into the relationship of genetics to dyslexia has been followed by a number of scientific research and personal observation reports through the past one hundred years. In 1976 Finucci found that in 45% of cases, immediate family members of the dyslexic person exhibited the same traits, confirming the belief that dyslexia runs in families. While in 1992, Dr B. Hornsby made the observation that 88% of the children treated by her had a family history of dyslexia. These studies and observations can be criticised for their lack of accounting for an environmental explanation (i.e. if one or both parents do not read well, then it could be argued that their children through a lack of parental modelling and guidance could "inherit" the same difficulties). Recent studies have attempted to overcome this f...