Tracking an occluded visual target with sequences of saccades
Tuisku Tammi1,2,3, Jami Pekkanen1,4, Samuel Tuhkanen1,5
1Cognitive Science, University of Helsinki, Helsinki, Finland.
Journal of Vision
|January 18, 2022
Summary
During visual tracking with occlusions, anticipatory saccades dominate, not smooth pursuit. This saccadic gaze behavior relies on an internal time-based position estimate, especially without external reference frames.
Area of Science:
- Neuroscience
- Ophthalmology
- Human-Computer Interaction
Background:
- Gaze behavior integrates smooth pursuit and saccadic movements for visual tracking.
- Object occlusion reduces smooth pursuit, increasing saccade reliance.
- Previous occlusion studies were limited to short durations and few saccades.
Purpose of the Study:
- Investigate visual tracking during extended random occlusions.
- Examine the role of anticipatory saccades and smooth pursuit.
- Analyze prediction uncertainty and reference frame effects.
Main Methods:
- Circular trajectory visual tracking task.
- Random, extended occlusion periods.
- Analysis of gaze behavior and prediction error accumulation.
Main Results:
- Reliable tracking up to several seconds during occlusion using primarily anticipatory saccades.
- Significantly reduced smooth pursuit during occlusions.
- Faster accumulation of prediction errors without an absolute reference frame.
Conclusions:
- Saccadic tracking during occlusion relies on an internal, time-based position estimate.
- This internal estimate is anchored to the environment via fixations.
- Absence of a reference frame enhances prediction uncertainty.
