The Influence of Saccade Predictability on Feature Binding after an Eye Movement
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Date
2024-05
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The Ohio State University
Abstract
People make multiple eye movements each second. These quick eye movements are referred to as saccades. These saccades can create shifts in perception that can create a dissimilarity between pre and post-saccadic retinotopic locations, disrupting visual stability. This discrepancy means post-saccadic remapping affects feature perception, creating some errors if there is insufficient time to update. Visual input is coded relative to its position on the eyes, or “retinotopic” coordinates naturally, but we often perceive objects to be in world-centered “spatiotopic” coordinates. When we move our eyes to a new location, an updating or remapping process is needed to reconcile visual inputs across the eye movement. Remapping is a process that can occur predictively, which may facilitate visual stability. However, remapping can also occur slowly, which might cause visual instability. This project is based on existing theories of spatial remapping and aims to answer the question: does predictability of a saccade influence object-feature binding after saccadic eye movements? For this eye-tracking study, the behavioral paradigm used by Golomb et al. (2014) was adopted: participants were cued to a target location and asked to report the color of the square occupying the cued target location after making a saccade. At different time points after a saccade, they were presented with an array of 4 colored squares at the cue’s spatiotopic and retinotopic locations and the two adjacent locations, creating a grid formation with equal eccentricity from fixation. We also manipulated saccade predictability; saccades in each block were predictable (e.g., clockwise and saccade cue onset after a fixed duration) or unpredictable (e.g., horizontal or vertical and saccade cue onset after a randomized duration). We expected to find a higher rate of systematic errors in the early delay condition compared to the late delay condition and an even greater difference between delay conditions in the unpredictable saccade condition. Our results showed improved general performance when saccades were predictable. Moreover, in the unpredictable saccade condition, there were “swap errors” at the early post-saccadic timepoint (short/early delay condition), a pattern reported previously where participants report the retinotopic non-target color instead of the correct spatiotopic target color. However, the swapping errors disappeared when saccades were made predictable. These results suggest that systematic color misperceptions associated with the retinotopic attentional trace may be malleable to top-down expectations of the upcoming saccade, highlighting the role of predictive coding in maintaining visual stability across saccades.
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remapping, spatial attention, feature errors, mixture-modeling, expectation