We review significant empirical studies of the arithmetic abilities of children with dyslexia. These studies suggest that the academic impairments of children with dyslexia are not limited to reading and spelling, but also include aspects of mathematics. A consistent finding across a number of studies is that children with dyslexia have difficulty recalling number facts. The results of the reviewed studies are analysed, both in terms of the weak phonological representations hypothesis, and the triple-code theory of mathematical cognition. It is suggested that the phonological processing deficits of individuals with dyslexia impair aspects of mathematics that rely on the manipulation of verbal codes (e.g. counting speed, number fact recall), whilst other aspects of mathematics that are less reliant on verbal codes (e.g. estimation, subitising) are unimpaired. Suggestions for testing this hypothesis are put forward.

This study examines the relationships between phonological awareness, visualspatial sketchpad (VSSP) functioning and arithmetic attainment in young children. A sample of 42 children had their VSSP functioning and phonological awareness assessed when they were 5 years old. Approximately 12 months later their nonverbal reasoning, vocabulary, arithmetic, and reading attainment were assessed. Together, VSSP functioning, phonological awareness, vocabulary, and nonverbal reasoning predicted 41% of the variation in the children's arithmetic attainment. Only phonological awareness and VSSP functioning were significant independent predictors. In contrast, only phonological awareness was a significant independent predictor of reading attainment. These findings are consistent with phonological awareness influencing both the development of reading and arithmetic, whilst VSSP functioning only impacts on arithmetic development.When children solve arithmetic problems they must generate and store either nonverbal or verbal representations of the quantities. Huttenlocher, Jordan, and Levine (1994) proposed that very young children use nonverbal mental models. Rasmussen and Bisanz (2005) further developed this proposal, arguing that young children's mental representations of quantities consist of a visual array of tokens that can be manipulated to perform arithmetic operations. They hypothesised that these visual representations are stored in the visual-spatial sketchpad (VSSP). Rasmussen and Bisanz suggest that as children progress through school they increasingly use verbal representations of quantities (i.e., number words), which are phonologically coded and can Correspondence should be addressed to Fiona Simmons,

The reading comprehension abilities of a group of dyslexic university students were compared with those of non-dyslexic university students. A 655-word passage, followed by literal and inferential questions, was used to measure reading comprehension. The text was designed to be syntactically complex, yet place relatively modest demands on decoding skills. Although dyslexic students performed at a similar level to the non-dyslexic students on the literal questions, their performance on the inferential questions was poorer. An index of the participants' ability to make inferences was calculated by subtracting the inferential question score from the literal question score. The groups differed significantly on this measure, indicating that the dyslexic students were specifically impaired in constructing inferences when processing complex text. It was concluded that dyslexic students in higher education have reading comprehension difficulties that cannot be accounted for by an inability to decode individual words in the text. The possible contribution that poor lexical automaticity and an impaired working memory make to this impairment is discussed. The implications for the assessment and support of dyslexic students are considered.

The relationship between dyslexia and visual stress (sometimes known as MearesIrlen syndrome) is uncertain. While some theorists have hypothesised an aetiological link between the two conditions, mediated by the magnocellular visual system, at the present time the predominant theories of dyslexia and visual stress see them as distinct, unrelated conditions, a view that has received some support from studies with children. Studies of visual stress in adults are rare, yet recent reports of a high incidence of this phenomenon amongst university students with diagnosed dyslexia call for further investigation of the issue. This study sought to clarify the relationship between visual stress and dyslexia by comparing the reading performance of dyslexic and non-dyslexic adults with, and without, colour. Degree of susceptibility to visual stress was determined by means of a symptom rating scale. Optimal colour was determined using an Intuitive Colorimeter, which was also employed to assess reading speed under the two experimental conditions. Only the dyslexic students with high visual stress showed significant gains in reading speed when using optimal colour. The use of response to treatment (rather than symptomatology) as a diagnostic criterion for visual stress is questioned, especially when applied to adults, as this may give misleading findings. On the basis of reported symptomatology, students who experience high levels of visual stress are more likely to show improvements in reading rate with optimal colour if they also have dyslexia than if they do not have dyslexia. Although not establishing an aetiological link, these findings imply an interaction between the two conditions with major implications for theory, diagnosis and treatment.The view that visual factors are involved in dyslexia has a long and controversial history. The current predominant theory -which is so well supported that it could be said to have acquired the status of orthodoxy -is that dyslexia is caused by a genetically-based anomaly in neurological systems sub-serving phonological processing (see

Identifying dyslexia in adulthood presents particular challenges because of complicating factors such as acquisition of compensatory strategies, differing degrees of intervention and the problem of distinguishing dyslexic adults from those whose literacy difficulties have non-cognitive causes. One of the implications is that conventional literacy measures, per se, do not provide a satisfactory basis for screening for dyslexia in adulthood as some dyslexic adults have above-average literacy skills and some non-dyslexic adults have very poor literacy skills. This study examined an alternative approach to dyslexia screening, using three tests that depend heavily on phonological processing, lexical access and working memory, but which are not conventional measures of literacy. Using these tests, which are computer delivered, 70 dyslexic adults from three different types of educational institution were compared with 69 non-dyslexic adults from the same institutions. The results showed that the dyslexic and non-dyslexic groups were significantly different on all three computer-based tests, with an average effect size of 1.55. Adaptive versions of these tests were then created to reduce overall administration time for the suite to about 15 minutes. Analysis showed that the combined scaled scores from the adaptive versions of the three tests significantly discriminated the dyslexic from the non-dyslexic group with an increased effect size of 2.07 and with a sensitivity rate of 90.6% and a specificity rate of 90.0%. It was concluded that this approach is a valid and useful method of identifying dyslexia in adulthood, which, given the ease of administration to large numbers of adults, has noted advantages for education and employment.