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Saeideh Ghahghaei, Preeti Verghese; Efficient saccade planning requires time and clear choices.. Journal of Vision 2014;14(10):1197. doi: 10.1167/14.10.1197.
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We move our eyes constantly to gather information. Saccades are efficient when they maximize the information required for the task, but evidence for efficient saccade planning is mixed. For example, eye movements are efficient when searching for a single target (Najemnik & Geisler, 2005), but are inefficient when searching for an unknown number of targets in noise, particularly under time pressure (Verghese, 2012). Here we examine whether saccades can be made more efficient by increasing the discriminability of target vs. distractor as well as by delaying the first saccade, so that decision processes can influence saccade planning. Methods: Observers actively searched a brief display (900 ms) with six Gabor patches to locate an unknown number of horizontal patches, among vertical distractor patches. Noise was added to the patches, making target /distractor identity harder to discern without a saccade to the patch. Each location had an independent probability of target, so the number of targets in a trial ranged from 0 to 6. We varied the prior probability of the target occurring at each location, from low to high in separate blocks. When the prior is high a saccade strategy that selects the noisy (uncertain) patches is more efficient. In separate experiments we 1) removed the noise from 50% of the patches to improve target-distractor discriminability and 2) delayed the first saccade to determine whether a longer inspection time would allow decision processes to influence saccade strategy. Results: A trial-by-trial analysis of observers saccades showed that when there was a discernible difference between clear and noisy patches, observers moved their eyes to the noisy patches to maximize information gained. Furthermore, this preference for uncertain locations was even more pronounced when the first saccade was delayed. Conclusion: Decision processes can influence longer latency saccade choices when the choices are clear.
Meeting abstract presented at VSS 2014
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