December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
What fixation durations reveal about the functional visual field in search through natural scenes
Author Affiliations & Notes
  • Daniel Ernst
    Brigham & Women’s Hospital / Harvard Medical School
    Bielefeld University
  • Jeremy Wolfe
    Brigham & Women’s Hospital / Harvard Medical School
  • Footnotes
    Acknowledgements  This research is funded by Deutsche Forschungsgemeinschaft (DFG, grant ER 962/1-1)
Journal of Vision December 2022, Vol.22, 3980. doi:
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      Daniel Ernst, Jeremy Wolfe; What fixation durations reveal about the functional visual field in search through natural scenes. Journal of Vision 2022;22(14):3980.

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

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An observer, fixating at one location, selectively processes stimuli in some surrounding region when searching for targets in visual search tasks. This region is called the functional visual field (FVF). Recent FVF research has sought to explain why observers sometimes miss a target even though they fixated nearby, placing the target clearly within the FVF. Such miss errors become especially important when the targets are, for example, tumors on x-rays or threats in baggage at airport security checkpoints. Understanding of such "look but fail to see" errors would benefit from a direct measure of the FVF during search. We use the duration of the “pre-target fixation” (PTF) as such a measure. The PTF is the fixation that immediately precedes a saccade to the target. In previous experiments where participants search for an O among Cs, PTF duration is shorter than other fixation durations when search is easy and when the target is near to the current fixation. It is hypothesized that the presence of a strong target signal inside the FVF speeds saccade planning and the resulting release of a saccade. In the present study, we tested whether similar effects can also be found in search through natural scene images where observers do not have precise target templates but only know the target category. To that end, we analyzed the large open source COCO-Search18 gaze dataset (Chen, Yang, Ahn, Samaras, Hoai, & Zelinsky, 2021). As in search for artificial stimuli, results showed shorter PTF durations if the target is close. As would be expected, the FVF as estimated from PTF duration is smaller when search is more difficult. The PTF duration method can be used to estimate the size of the FVF in a manner more natural and more convenient than gaze contingent moving window paradigms.


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