Reading Development and Reading Disability: Analyses of eye-movements and word recognition
Sammanfattning: The primary ambition of this doctoral thesis is to provide an empirical basis for a better understanding of reading disability among school children. The current consensus in the research community is that most disabled readers fail in the acquisition of fast, accurate and automatic word recognition. The thesis includes a number of studies where normal and disabled readers are compared on various aspects of visual word recognition and related processes. The participants, about 100 disabled readers and 90 normal readers, were selected from a full cohort of 2nd graders (N = 2165) in the county of Kronoberg, Sweden, and were carefully matched on gender, non-verbal intelligence and school class. Extensive assessments of reading and spelling, cognitive ability, vision, eye movements, motor skill and socio-economic background were carried out as well as teachers’ ratings of school behaviour. First, basic visual functions, including eye movements, were examined. Only minor differences between the groups were observed, such as a slightly lower contrast sensitivity and poorer control of binocular saccades among the reading disabled children. Some of the small differences in visual functions could be interpreted as reflecting differences in attention mechanisms. A new group test for assessing the growth of word recognition skill was developed; the Wordchains test. The course of development of word reading skill was examined in a cross-sectional study covering the whole period of compulsory schooling. A modified quadratic function yielded the best fit to the data, and the asymptote level was reached around the age of 18. Girls outperformed boys at all stages. A longitudinal study gave support for a deficit model of reading disability. In summary, 3 out of 5 of the children initially classified as reading disabled were stable poor readers seven years later. Only a minority (18%) followed a lag model, reaching a normal level by grade 9. For the reading disabled boys a growth curve analysis demonstrated that about 25% of the variance in slope (average rate of individual growth) could be explained by factors related to early reading skill and non-verbal intelligence. A wide range of neuropsychological and social variables failed to predict individual development in word reading. For the control group none of the independent variables explained the slope variance. Methodological issues involved in the growth study were analysed and discussed.
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