Biological level

There is considerable evidence to support the view that dyslexia is a condition with a genetic origin and a biological basis in the brain. Dyslexia is more common in males and tends to run in families (Hermann, 1959). There is also evidence of physiological brain differences between dyslexics and non-dyslexics while they are reading or doing reading-related tasks (e.g. Brunswick et al., 1999; Paulesu et al., 2001). There has been considerable research that links dyslexia to differences in the form and function of the right and left hemispheres of the brain. It has been found that 75 per cent of human brains are asymmetrical but that the brains of dyslexics are more likely to be symmetrical. It had initially been believed that language, both spoken and written, is mediated by the left cerebral hemisphere and visuo-spatial perception by the right cerebral hemisphere. This had led to a ‘balance model of reading’ that describes reading as the developmental integration of two processes:

1 The perceptual analysis of text features. This is needed in order to establish how letter shapes make up text e.g. letters may be reversed and have different meaning (e.g. ‘b’ and ‘d’), but different shapes could be the same letter (‘b’ and ‘B’). The development of this early reading skill involves considerable right hemisphere processing and reading fluency involves automatization of this skill.

2 The linguistic analysis of text. As the child ‘automates’ the perceptual aspect of reading, he/she becomes more acquainted with the syntactic rules and his/her vocabulary grows as reading progresses. As a consequence, the child does not read letter-by-letter or syllable-by-syllable but by processes. The balance model of reading holds that fluent reading that is developed by use of syntactical rules and linguistic experience is predominantly guided by the left cerebral hemisphere.

In ‘normal’ development it is proposed that the right hemisphere guides early reading initially and then the left hemisphere predominates. There is evidence to support the view that ‘right’ and ‘left’ hemisphere differences provide a useful explanatory basis for some of the differences observed in the development of reading fluency between dyslexic and non-dyslexic individuals. However, this explanation is not as clear-cut as originally conceived due to findings that question the clear and stable delineation of right and left hemisphere functions into ‘perceptual’ and ‘language’ respectively (Fagaloni et al., 1969). In addition to exhibiting differences in the development of reading, particularly in the development of ‘automaticity’, differences in form and function of the brain and hemispheric activity are thought to contribute to the fact that dyslexics often exhibit difficulties with sequencing, synthesizing information and with overall organization. The biological basis of dyslexia remains a fertile area of research and neuropsychological intervention (Robertson and Bakker, 2002) and is increasingly likely to be seen as a useful addition to the repertoire of specialist teaching approaches available for dyslexic pupils. In essence, approaches that stimulate ‘weaker’ areas of processing, and improve synthesis between right and left brain activities (i.e. perceptual and language processing) are likely to be useful. Other implications arising from ‘biological’ representation of dyslexia are:

■ Early identification via use of family history, possible use of technologies (e.g. positron emission tomography (PET) and magnetic resonance imaging, (MRI)).

■ Understanding that dyslexia is ‘lifelong’ and cannot be ‘cured’ but barriers to achievement can be identified and reduced.

■ Some specialist programs based on ‘biological’ explanations of dyslexia that seek to reduce development differences and delays and enhance overall synthesis of brain functions, i.e. movement, memory, language and perception etc. (Hemisphere Specific Stimulation Programs (HEMSTIM) (Bakker and Vinke, 1985), Brain Gym (Dennison and Hargrove, 1986), Mind mapping (Buzan, 1993)).

■ The achievement of increased ‘fluency’ in written language is the aim of many specialist programs for dyslexics. This requires attention to the development of automaticity of the perceptual analysis of text. Hence specialist programs are usually phonic-based and seek to use multi-sensory techniques, structured approaches, and opportunities for over-learning (e.g. Hickey Multi-sensory Language Program (Augur and Briggs, 1992). The National Literacy Strategy (DfES, 1998) and linked support materials seek to achieve ‘automatic’ perceptual analysis of text through structured ‘word level work’.

■ The need to be sensitive to the grouping of pupils with dyslexia to ensure that even if they have difficulties with ‘perceptual analysis’ of text (word level work) that the opportunity to develop their vocabulary and syntactic knowledge is made available to them. Ensuring that dyslexics have access to written language commensurate with their comprehension level is important by reading to them (peers/parents) or listening to story tapes, etc.

■ The importance of monitoring pupil response to teaching in order to identify differences or difficulties that he/she may have with synthesizing perceptual and linguistic features of text, e.g. miscue analysis.