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Scott Watamaniuk, Stephen Heinen; Distractors enhance target detection during smooth pursuit. Journal of Vision 2007;7(9):1009. doi: 10.1167/7.9.1009.
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The presence of distractors in a visual scene typically impairs target detection. Here, we show that embedding a target stimulus in a field of dots improves observers' ability to detect a ‘blink’ in a moving target stimulus. The target stimulus was comprised of five, small (0.2 deg) bright spots arranged in a ‘+’ configuration with a 6 deg horizontal and vertical extent. At the beginning of each trial, the target appeared and the observer fixated the center spot. After a random fixation period, the five-spot target began to move at a constant speed (10–30 deg/sec). At a randomly selected time, (between 100–500 msec), one of the 5 spots was dimmed briefly (170 msec) before returning to its original luminance. The observer's task was to identify which of the spots was dimmed. The five-spot target was presented either on a homogeneous gray background, or one composed of 500 dots of the same diameter, but with slightly lower luminance. Background dots were randomly positioned within a large rectangular aperture but excluded from the target area. When present, the background moved at the same velocity as the target. Surprisingly, target detection was improved by the presence of the moving background in that observers correctly identified the blinked target more frequently in this condition than when the target stimulus moved in isolation. This appeared at least partly due to enhanced smooth pursuit eye movements that were less variable and contaminated by fewer catch-up saccades in the background-on condition. This finding is consistent with our previous work on pursuit of random-dot cinematograms (Heinen & Watamaniuk, 1998). The results suggest that large, textured objects stimulate a different pursuit system than that previously studied using a single spot, which may have evolved to provide image stabilization to allow detection and discrimination of object features.
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