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Preeti Verghese, Saeideh Ghahghaei; Immediate feedback improves saccadic efficiency. Journal of Vision 2013;13(9):302. doi: https://doi.org/10.1167/13.9.302.
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When the task is to find multiple targets in a limited time, saccades need to be efficient to maximize the information gained. In theory, selecting uncertain locations is much more informative than selecting locations most likely to have the target. Contrary to this prediction, previous work has shown that observers fixated likely target locations while searching for multiple targets in noise. Saccade efficiency did not improve despite extensive training with full feedback at the end of each trial (Verghese, 2012). Here we examined whether immediate feedback following each saccade improved saccade strategy. Observers actively searched a display with six disks equally spaced around a 3° eccentric circle. Each location had an independent probability of a signal, so the number of signal disks in a trial ranged from 0 to 6. The luminance of each disk was drawn randomly from Gaussian distributions of signal and noise, with mean separation and standard deviation 5 and 3.33 cd/m[sup]2[/sup], respectively. Due to the overlap of the distributions, it was uncertain whether a luminance value in the overlap zone came from signal or noise distribution. As an incentive to explore uncertain locations, a saccade to a disk with luminance in the overlap zone generated immediate feedback by switching the disk luminance to the mean value of the "true" distribution. At the end of the 1150 ms display, observers selected all potential signal locations with a cursor. We performed a trial-by-trial analysis of observers’ saccades to determine saccade strategy. Initially all observers (n=4) made saccades to likely locations, as in the previous study using delayed feedback. However modest practice with immediate feedback resulted in significant changes to saccade strategy. Observers made more efficient saccades, selecting uncertain locations over likely locations. These findings indicate that immediate feedback is very effective in increasing the efficiency of eye movements.
Meeting abstract presented at VSS 2013
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