Top-down control and onset capture: the role of early feature-specific modulation

Lewis, Amanda (2012). Top-down control and onset capture: the role of early feature-specific modulation Honours Thesis, School of Psychology, The University of Queensland.

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Author Lewis, Amanda
Thesis Title Top-down control and onset capture: the role of early feature-specific modulation
School, Centre or Institute School of Psychology
Institution The University of Queensland
Publication date 2012-10-10
Thesis type Honours Thesis
Supervisor Stefanie Becker
Total pages 76
Language eng
Subjects 1701 Psychology
Abstract/Summary Two experiments were conducted to investigate the capture of attention by suddenly appearing items (‘onsets’) in visual search. A wide-spread view is that onsets capture attention in a purely stimulus-driven manner, against the top-down goals of an observer. Yet, some studies have shown that onset distractors capture the eyes more strongly when they are similar to the soughtafter target, indicating that onset capture can be modulated by top-down processes. However, it is still unclear how or when top-down controlled processes start to modulate onset capture. One hypothesis is that top-down controlled processes play a role at a later stage of processing, subsequent to stimulus-driven control. The present study examined these two questions in two eye tracking experiments where participants had to make a fast eye movement to a target while ignoring an onset distractor. To examine whether top- down control consists in target activation or distractor suppression, onset distractors were presented in different colours. The time-course of top-down control was investigated by presenting distractors of different colours before or after the target display, using a Stimulus Onset Asynchrony. The results showed that both target activation and distractor inhibition modulated onset capture, from an early stage of visual processing. Moreover, a pure onset which is salient only by virtue of its onset and not colour, captured only when it was presented prior to the target display, not when it was presented simultaneously with the target. The results showed that top-down processes modulate onset capture from an early stage of visual processing.
Keyword Top-down control
Onset capture
Feature-specific modulation

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Created: Tue, 05 Mar 2013, 14:34:51 EST by Mrs Ann Lee on behalf of School of Psychology