AbstractsPsychology

This thesis applied a choice reaching task (CRT) to different visual search settings to investigate the temporal characteristics of visual attention. The initiation latency (IL) and maximum deviation (MD) of the reach trajectory provided the greatest insight into early and ongoing competition for selection. We replicated priming of pop-out (PoP) effects on IL and MD before using the PoP paradigm to examine motor system involvement in generating movement-relevant predictions. Predictable repetition of the target colour recruited the motor cortex but only when the colour signalled the target of an overt movement. We also demonstrated that reaches are affected by global-to-local scene processing presenting a novel dissociation of IL and MD. IL reflected global configural biases (bottom-up), whilst MD reflected local positional biases (top-down). Finally, we examined the influence of irrelevant features (IFs) on target selection. Attentional capture by the IF affected the entire selection process when the target colour and IF presence were unpredictable. When the IF could coincide with multiple search items performance was modulated by early proximity and late similarity grouping. Overall, the results demonstrate the ability of the CRT to investigate the time course of attentional processing above and beyond that provided by key-press response tasks.