Saccadic efficiency in visual search for multiple targets P Verghese |
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Smith-Kettlewell Eye Research Institute, CA, United States
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| We investigated saccadic targeting when observers actively searched a display to find an unknown number of targets. Search time was limited, so saccades needed to be efficient to maximize the information gained. As there was insufficient time to examine all potential target locations, selecting uncertain locations was much more informative than selecting likely target locations; saccades to uncertain locations could resolve whether a target was present, whereas a saccade to likely target locations provided little additional information. Observers actively searched a display with six potential target locations embedded in noise. At the end of a brief display (1150 ms), observers reported all locations with a target. Each location had an independent probability of having a target, so the number of targets varied from 0 to 6 from trial to trial. Contrary to the prediction for maximizing information, observers made saccades to likely target locations, rather than to uncertain locations. Full feedback after each trial did not improve saccadic efficiency. We therefore examined whether immediate feedback following each saccade improved performance. Modest practice with immediate feedback resulted in significant improvements in saccadic efficiency, suggesting that observers were able to overcome partially a natural tendency to saccade to likely target locations. |
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