Title:
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Movement interference in visuo-spatial working memory
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This thesis sets out to examine movement interference in visuo-spatial working memory within the framework of the Baddeley & Hitch model of Working Memory (WM). Many studies have shown that concurrent movement interferes with visuo-spatial processing with interference being mainly marked during active encoding rather during image maintenance. However, it is not clear whether concurrent movement interferes because both tasks share a common visuo-spatial resource or whether interference is due to the involvement of the hypothetical Central Executive (CE). This study approached this issue via the most widely used task, the Brooks Matrix. After reviewing the evidence which led to the abandonment of the notion of a unitary system and to the proposal of a multi-component model of WM, evidence was then reviewed for the existence of a specialised subsystem, the Visuo-Spatial Scratchpad (VSSP), dealing with the temporary processing of visuo-spatial information and images and that is linked to the planning and control of movement. After reviewing the literature on the VSSP and presenting evidence for the difficulty of the Brooks Matrix task, the thesis moves on to systematically examine the cognitive processes involved in performance of this task. A process- model is then proposed which combines features of both the WM model and Annett's Action, Language & Imagination model. The CE is assigned specific roles in image generation and verbal encoding of the task. Subsequent experiments, using movement interference paradigms, examined the interference effects of various movement tasks on the Brooks Matrix task or on new simplified variants that were assumed to minimise CE involvement. Movement interference was examined during both the encoding and the maintenance stages. Two broad issues were explored, the relationship between the VSSP and the CE, and the nature of the refresh mechanism in the VSSP. The overall results point to the importance of the CE in visuo-spatial processing and support previous indications that the CE is 'coupled' to the VSSP during active processing. Further, the results appear to indirectly lend support to the notion that the VSSP may indeed comprise two separable spatial and visual subsystems. Finally, the results did not support the proposal of a 'motoric' refresh mechanism in the VSSP that is analogous to the refresh mechanism in verbal WM. Whether subjective reports of imagery vividness correlate with performance on the Brooks visuo-spatial task was examined by the use of the VMIQ and WIQ questionnaires. Inconsistent results were obtained and a discussion of this issue is provided. The thesis concludes with a discussion of the implications of the overall results to the structure of WM and suggests that further research into movement interference in visuo-spatial WM is needed until a full understanding of the link between spatial representation and motor control is reached. Tasks developed here including new variants on the Brooks Matrix task and some secondary tasks may be used in future research. Finally, the thesis concludes with pointing out the importance of understanding how movements and actions are represented in WM to the acquisition of motor skills.
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