2.3.1 Sex differences
An intriguing aspect of dyslexia is the apparent excess of males who are affected. This could simply reflect referral bias – a tendency for boys to be identified as dyslexic more readily than girls. In the past, society's expectations of boys and girls were very different with respect to educational achievement. There is now much less overt stereotyping of this kind, but there may still be other reasons why dyslexia might be more readily identified in boys. For example, evidence suggests that in mixed-sex classes, boys often dominate classroom interactions. This might bring their general ability to the attention of teachers, who could fail to notice the abilities of some quieter girls whose reading attainment is equally discrepant. Another possibility is that boys and girls may respond differently to the experience of reading failure, with boys perhaps more likely to ‘externalise’ their frustrations over their reading difficulties than girls. Even awareness that dyslexia is more common in boys could serve to influence the expectations of parents, teachers and others, thereby creating something of a ‘self-fulfilling prophecy’.
Nevertheless, the evidence does suggest that as many as three or four males may be affected for every female (James, 1992). This apparent sex difference still awaits adequate explanation, especially given evidence from a recent twin study that found no gender difference in heritability of reading difficulties (Wadsworth et al., 2000). In some respects, the excess of males with dyslexia appears to be an exaggeration of the usual slight advantage that females, on average, tend to show for language-related skills. Boys appear to show greater visual-spatial awareness than girls do, and you may wonder why these skills do not offer any advantage for processing written language. However, as we have already observed, visual- spatial awareness does not prohibit the development of visual- perceptual difficulties that are associated with dyslexia. Males are over-represented to varying degrees across a whole range of developmental disorders. These include not only dyslexia, but also dysphasia, dyspraxia, ADHD and the autistic spectrum of disorders. What is more, all of these conditions tend to run in families, suggesting that they might share at least some common elements at the level of biological predisposition.