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Bilge Sayim, Patrick Cavanagh; Effects of target-flanker grouping in crowding inside and outside the critical spacing. Journal of Vision 2011;11(11):1157. doi: 10.1167/11.11.1157.
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Peripheral target perception is impaired by close-by flankers, an interference that is called crowding. For example, discriminating the orientation of a rotated letter T is compromised when it is flanked by other Ts. Besides target-flanker distance, an important factor that determines crowding is the degree to which target and flankers group: The more the target groups with the flankers, the stronger the crowding (e.g., Saarela, Sayim, Westheimer, & Herzog, 2009). Here, we investigate whether target-flanker grouping can also alleviate crowding. A target letter T had two sets of flankers making a cross shape with the target in the center. The first set were “crowding-flankers” with two Ts of varying orientations placed to the left and right side of the target. The second set were “grouping-flankers” both with the same orientation placed above and below the target. In the grouped condition, the target had the same orientation as the grouping-flankers whereas in the ungrouped condition, the target had a different orientation from the grouping-flankers. Observers reported the orientation of the target. The proportion correct was higher in the grouped compared to the ungrouped condition indicating that grouping-flankers counteract crowding. This effect was observed even when the grouping-flankers were presented outside the critical spacing for crowding (too far from the target to yield crowding). Further experiments showed that in the grouped condition, both hits and false alarms increased showing a bias to reporting the target as having the same orientation as the grouping flankers. We suggest that this bias reflects perceptual assimilation of the target with the grouped items.
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