2.6 Environmental explanations of dyslexia?
‘Environment’ is often used to refer to only social or non-biological influences. However, it actually also refers to the biological, cognitive and behavioural environments that we may be exposed to. If you refer back to Frith's framework (see Figure 2) you will remember that the environment can be heavily involved in each perspective. An example of a biological environmental influence is a dietary deficiency such as insufficient consumption of fatty acids. The idea that dyslexia has a non-biological environmental explanation has been excluded: you may recall that external environmental factors were explicitly rejected in exclusion based definitions of dyslexia. However, Spear-Swerling and Sternberg (1998) believe that there is some evidence to suggest that while such factors may not explain dyslexia, they can dramatically affect the nature and extent of the difficulties experienced. For example, Adams (1990) has suggested that reading aloud to preschool children results in real benefits in later reading development. Snow (1991) found that children who have a ‘literate home environment’ were more likely to progress in reading than peers who were exposed to less ‘literate’ contexts. MacLean et al. (1987) have also shown that children's knowledge of nursery rhymes can predict both reading performance and phonological awareness.
Just as the home environment can influence reading development, so too can school environments. For example, children are exposed to different methods of reading instruction and it has been argued that some instructional methods can effectively prevent reading difficulties (Clay, 1990). Similarly, the overemphasis on either phonic (alphabetic) or whole word (logographic) approaches to reading can exacerbate existing reading difficulties, because of the need for both skills to compensate for the relative weaknesses of each approach (Chall, 1996). Anderson et al. (1985) have also found evidence that children who are ‘streamed’ into low ability groups receive less effective instruction due to lower expectations of what they can be expected to achieve. There is also often a higher incidence of behavioural difficulties in such groups, which can disrupt opportunities for learning.
… we cannot blame reading failure – especially extreme disability – on either the child or the initial method alone. Severe disability seems to result when a child has a predisposition (a set of characteristics that make it difficult for him to associate printed symbols with their spoken counterparts) and is exposed to an initial method that ignores this predisposition.
(Chall, 1996, p. 175)