October 2020
Volume 20, Issue 11
Open Access
Vision Sciences Society Annual Meeting Abstract  |   October 2020
Spatiotemporal dynamics of foveal visual search
Author Affiliations & Notes
  • Sanjana kapisthalam
    University of Rochester
  • Martina Poletti
    University of Rochester
  • Footnotes
    Acknowledgements  funded by Facebook, Inc.
Journal of Vision October 2020, Vol.20, 885. doi:https://doi.org/10.1167/jov.20.11.885
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      Sanjana kapisthalam, Martina Poletti; Spatiotemporal dynamics of foveal visual search. Journal of Vision 2020;20(11):885. doi: https://doi.org/10.1167/jov.20.11.885.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

The concept of visual search is normally associated with large saccades, which are used to explore the visual scene by placing the high-resolution fovea on the stimuli of interest. However, we previously showed that, once the object of interest is foveated, observers engage in active exploration of foveal details using precisely guided microsaccades. Here we investigated the spatiotemporal dynamics of foveal exploration, and the contribution of top-down and bottom-up factors in driving visual search at this scale. Subjects (n = 8) were instructed to search for a target, a small tilted bar (1x8 arcminutes in size), in an array of 7 similar items presented foveally. The search array spanned 0.5 deg, approximately half of the size of the foveola, and was presented for 1s. The task-relevance and salience of each item in the array was manipulated independently. Salience was modulated by changing the contrast level of the stimuli, whereas task relevance was modulated by changing the similarity of each item to the target. Gaze position was tracked by means of a high-precision eyetracker. Our results show that, even if all the stimuli were presented foveally, subjects engage in active visual search, using microsaccades as small as 10 arcminutes. When multiple items of similar relevance are present in the foveal landscape, it takes approximately 500ms for the system to establish a priority map and drive an eye movement toward the search target. This time is reduced on average by 150ms, and the accuracy of fine oculomotor behavior is increased, when the target is perceptually salient. Furthermore, salient distractors do not appear to influence oculomotor behavior and performance in the task. These findings suggest that the search pattern is modulated by saliency at the foveal scale, and that salient distractors are actively inhibited at no-cost for the visual system during foveal search.

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