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Jeremy M Wolfe, Chia-Chien Wu, Jonathon Li, Sneha B Suresh; Missing what is right in front of our eyes. Journal of Vision 2021;21(9):2073. doi: https://doi.org/10.1167/jov.21.9.2073.
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© ARVO (1962-2015); The Authors (2016-present)
When we search for something in a scene, it is obvious that we are more likely to find that target in the next moments if it is near fixation. This is true even if items are large and well-separated and is even more evident in any real-world, cluttered scene. This notion of a searchable region of processing around the point of fixation is formalized as the “Useful Field of View” (UFOV) or Functional Visual Field (FVF). We might assume that, if a simple target falls inside the current FVF, it will be found and fixated by the next saccade, but this is not the case. We recorded eye movements as 22 observers searched for Ts in a grid-like display of Ls. For each fixation, we measured the distance to the target and calculated the probability that the next saccade would go to the target. Even when the target was a neighboring item (<2 deg away), that probability was about 45%. Two degrees is well within any estimate of the FVF radius for these stimuli. If the task is made harder, probability drops to 34%. If the criteria are loosened to include any of the next 3 fixations (to allow for corrective saccades, etc), probability only rises to 68%. Similar results were obtained for 18 radiologists reading mammograms. The FVF defines a region where a target CAN be found but the need to selectively attend to individual items means that detectable items may not be detected. At the same time, introspection assures us that we have looked at the fixated region. Hence, we can be surprised when we fail to find targets in places where we believe that we have searched.
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