Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Psychology

Language

English (en)

Date of Award

January 2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Richard Abrams

Abstract

Previous studies have shown that an irrelevant distractor matched to a sought-for color captures attention involuntarily, thus violating either temporal or spatial control of attention. However, whether an irrelevant distractor that matches a sought-for orientation can capture attention is still unknown. A task of rapid serial visual presentation: RSVP) was developed to examine whether an irrelevant distractor oriented in the same way as the target can capture attention. Participants were presented with a sequence of letters at fixation and were required to search for the target letter with a specific orientation. In all five experiments, six peripheral bars flanked the central letters either shortly before or after the appearance of the target letter. The present study found that six homogeneously oriented bars in the periphery: 45 degrees from the sought-for orientation) did not impair target performance compared to no peripheral bars at all. However, a peripheral orientation singleton that matched the target orientation captured attention and severely impaired central target identification. In addition, a peripheral orientation singleton that was orthogonal to the target orientation also captured attention and produced a similar impairment as the orientation-matched distractor. And the capture effect by the orthogonal singleton: 90 degrees from the sought-for orientation) was not due to the stimulus-driven saliency of an orientation singleton because a horizontal singleton: 45 degrees from the sought-for orientation) did not capture attention in this task. In addition, an orientation singleton that was perpendicular to the target orientation still captured attention when two orthogonal letters that were perpendicular to the target orientation appeared in the central stream. Thus participants did not prioritize the orthogonal orientation: 90 degrees from the sought-for orientation) for its single occurrence in the central stream. The results indicate that a top-down control setting for a specific orientation does exist, but the orientation-based modulation of attention is not as perfectly tuned to target as color-based modulation. The unexpected capture by orthogonal distractors is likely due to the special characteristic of orientation tuning curves of visual neurons. Some studies showed that a proportion of V2 and V3 neurons in monkeys have bimodal orientation tuning curves with two peaks 90 degrees apart: Anzai, Peng & Van Essen, 2007; Felleman & Van Essen, 1987). The present results are consistent with those single cell recording studies. Thus the present results indicate that feature preferences of visual neurons also play an important role in the feature-based attentional modulation. The allocation of feature-based attention is determined by a joint effect of three components including top-down guidance, stimulus saliency and feature preference of visual neurons.

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Permanent URL: http://dx.doi.org/10.7936/K7FJ2DW5

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