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Individual differences in WMC predict performance on everyday cognitive tasks, and measures of general intelligence (e.g. Conway, Kane, & Engle, 2003). Previous attempts to identify WMC-related differences on more specific functions that may contribute to the differential abilities between high and low WMC individuals have been mostly restricted to executive attention tasks (e.g. Kane et aI., 2007). Although external cognitive load, and exogenous orienting events, have both been reported to influence higher order functions (such as selective attention; Lavie et aI., 2004, and memory encoding; Schmidt and Vogel, 2002), the potential differential effects of these factors on high and low WMC individuals have not been addressed previously. In Section 1 of the thesis the interactive effects of external WM load and WMC on visual selective attention efficiency were investigated in the Navon and Flanker tasks; a reliable interactive effect of these factors on task performance was observed. The pattern of results implies that limitations in cognitive resources (either due to individual differences or external load) affect the ability to effectively constrain attention to relevant information. In Section 2, WMC-related differences in exogenous orienting were investigated using the ANT, Posner cueing task, and Gap paradigm. A reliable difference in high and low WMC individuals' orienting response was recorded in these tasks, but arguably only when the bottom-up exogenous orienting response was amenable to enhancement via top-down influences. Collectively the work has advanced understanding of WMC-related variations in visual attention processes; the findings from Section 1 not only document WMC-related differences in visual selective attention but also provide a mechanistic explanation for the variation, whilst the Section 2 findings revealed a WMC-related variation in utilisation of top-down on bottom-up effects during exogenous attentional orienting. The results have connotations for current theories of WMC and visual selective attention, which are discussed accordingly. |
