UBC Theses and Dissertations
Anisotropy of covert, endogenous orienting of attention across the visual field Roggeveen, Alexa Bleiweis
Are there advantages to voluntarily attending to some visual field locations over others? The work discussed here explores the question of whether covert, endogenous (voluntary) orienting to various visual field locations has anisotropic effects. Important to this question is understanding how paradigm parameters alter the way that attention is voluntarily distributed across possible target locations, and how that ultimately affects the anisotropy of performance at different visual field locations. When observers are cued to attend with 100% certainty to a visual field location, the effects of endogenous orienting run parallel to previous findings of perceptual and attentional anisotropy (vertical anisotropy; horizontal vs. vertical meridian). This is the first work to demonstrate an attentional benefit to voluntarily attending to the vertical meridian compared to the horizontal meridian. Lowering the cue's predictive value altered the pattern of anisotropic performance, revealing that attention had varying impact with distance from fixation, as well as a greater impact on the lower half of the vertical meridian. This result reflects how attention was distributed across possible target locations in the display, given that the target may not appear at the cued location. Further experiments showed that task parameters have a distinct effect on how attention is distributed across possible target locations. Altering the endogenous distribution of attention by eliminating or reducing an inhibitory gradient at fixation affects performance to the greatest degree close to fixation, and on the horizontal meridian. Both experiments are also the first to reveal an attentional oblique effect, whereby response time to targets presented on the intercardinal axes is consistently and significantly slower than on the cardinal axes. A key role is also demonstrated for the use of placeholders (perceptual objects) which facilitate the objects) which facilitate the voluntary distribution of attention across possible target locations. The effect of placeholders interacts with the cue's predictive value to alter how attention is voluntarily distributed across possible target locations. Overall, the answer to the overarching question is yes: covert, endogenous orienting has anisotropic effects. In light of these findings, four general guidelines are presented to illustrate the impact of covert, endogenous distribution of attention across the visual field.
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