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    Representing space: the development, content and accuracy of mental representations by the blind and visually impaired

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    This thesis reports on two studies on the perception and cognition of space by individuals who are blind and visually impaired. Research was conducted with students from Dorton College at the Royal London Society for the Blind (RLSB) in Kent. The first experiment examined the content and accuracy of mental representations of a well-known environment. Students walked a route around the RLSB campus and learned the position of ten buildings and structures. They were then asked to make pointing judgments, estimate distances and complete a spatial cued model of the campus. The second experiment considered the wayflnding strategies and spatial coding heuristics used to explore a complex novel environment. Students were asked to explore a maze and learn the position of six different locations. Their search patterns were recorded and analyzed using Geographic Information Systems (GIS) software. Students were tested using the same methods as in the previous experiment and their performance was related to the type and frequency of strategies used during exploration. Results were complemented with a mobility questionnaire, a low vision quality of life questionnaire and data from a literacy and numeracy assessment as well as ethnographic material collected by the author during the two years spent working and living at the RLSB. The thesis begins with a discussion of disability and society framed within the context of geography, urban planning and design. The concepts of blindness and visual impairment are then examined with particular attention given to the psychosocial implications of visual loss. This is followed by a discussion of growth and development, and in-depth review of research on the development, content and accuracy of mental representations by the blind and visually impaired. Finally, the methods used to collect and analyse data for both experiments are considered in light of individual differences and the inadequacy of some statistical techniques to account for the heterogeneous nature of visual impairment. Results from the first experiment revealed significant differences in the accuracy and content of mental representation between the sighted, visually impaired and blind groups for the pointing and model construction tasks. Performance in the distance estimation task was similar across groups. Large individual differences were identified, with the performance of individuals in the same group varying according to the type and requirement of the task. Results from the second experiment also revealed significant differences between the different groups, this time for all three tasks. Here again, large individual differences were found within each group. An analysis of distortions revealed that despite a disparity in accuracy, the blind and visually impaired shared many of the systematic distortions typically found in the mental representation of sighted individuals further confirming their ability develop functional mental representations of space. Performance in the pointing, distance estimation and model construction tasks were also related to the type and frequency of strategies used to explore the maze with the best performers using a combination of egocentric and allocentric strategies. In general, results from the two experiments support the amodal notion that the construction of accurate mental representations of space is not limited to any particular sensory modality but facilitated by the visual system. It also emphasizes the need for mutually supportive techniques that incorporate both quantitative and qualitative methods in the collection and analysis of cognitive data