EFFECTS OF CONTRAST ON PERCEPTION IN DISABLED READERS

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Recent experiments with reading disabled children have shown that image blurring results in an immediate benefit in search performance, eye movement pattern and reading comprehension. This suggests that the contrast and spatial frequency content of visual stimuli are important factors for these children. The proposed research will assess the effects of contrast and spatial frequency content on visual processing in normal and disabled readers. Normal and reading disabled children will be classified through the use of individually administered reading tests. They will also undergo a battery of screening tests involving visual, auditory, intellectual, and neuropsychological assessment to evaluate their overall status. The children will take part in an experiment designed to measure the effects of spatial filtering and contrast reduction on visual search. This experiment will provide information on whether the previously demonstrated benefit of contrast reduction occurs for all spatial frequencies or is restricted to a limited range of spatial frequencies. In a second experiment using the same children, the contrast gain associated with different spatial frequencies will be assessed using a contrast matching paradigm. This experiment will allow a more precise interpretation of the first experiment and provide information on the range of contrasts that are important for contrast reduction effects. In the third experiment, the children's movement detection sensitivity will be measured at various spatial frequencies. This experiment will determine if contrast gain problems are associated with decreased movement detection. The fourth experiment will examine spatial location ability using targets of different contrast. This experiment will determine if contrast gain problems are associated with previously reported spatial location discrepancies in poor readers. The results of these four experiments will provide valuable information about the nature of the visual deficit in reading disabled children and elucidate the major factors involved in existing remedial techniques.