Date of Award

2002

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Kinesiology

Supervisor

Professor Digby Elliott

Abstract

Fundamental to the theories of action-based attention is the notion that response-producing processes are automatically initiated when an object receives attention. In support of action-based theories, movement trajectories have been found to deviate in the presence of non-target stimuli even when the stimuli do not present a physical barrier to the movement (Howard & Tipper, 1997; Welsh, Elliott, & Weeks, 1999). A model of response activation has been proposed to explain these deviations. Predictions based on the model are that, if a response is active at the moment of response activation, then the response will contain characteristics of both the target and non-target response. If the non-target response is inhibited at the time of response initiation, then the response will contain characteristics that are opposite to the non-target response. The five experiments reported in this dissertation were designed to test this model. In the first experiment, it was found that the trajectories of the rapid-aiming movement to a target location deviated towards the location of a simultaneously presented non-target stimulus. This finding replicated earlier work (Welsh et aI., 1999). The results of the second experiment supported the hypothesis that movement deviation away from the location of the non-target stimulus was the result of inhibition of the response to that stimulus. In the third experiment, the target location was precued to examine the effects of response priming on selective action. Consistent with predictions, when the target response was validly cued, no significant distractor interference was observed. On the other hand, if the distractor was presented at the cued location while the target was presented elsewhere, then the movement veered towards the location of the distractor. A similar precuing methodology was employed in the fourth experiment to explore the effects that response priming and inhibition associated with valid and invalid cues have on the trajectory of the target movement when the target is presented in isolation (without a simultaneously presented non-target stimulus). The results of this experiment were generally congruent with the model of response activation. The final study was designed to examine how inhibitory processes, hypothesized to be associated with negative priming and inhibition of return, would affect movement preparation and execution. Consistent with previous work, the presence of the distractor in the prime trials caused deviations in the movement trajectories towards the location of the non-target stimulus. Inhibition of return and negative priming effects, however, were not found. Facilitation effects associated with colour repetition and the lack of competition in the probe trials were the likely causes underlying these latter null effects. Overall, the results of the present series of studies suggest that the model of response activation is able to predict deviations in the path of aiming movements under competitive conditions. Development of the model in terms of the interaction between perception and action systems is required to enable it to account for all effects associated with selective attention.

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