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Paper   IPM / Cognitive / 7596
School of Cognitive Sciences
  Title:   Distance dependent compulsory averaging of crowded signals
1.  L. Montaser kouhsari
2.  H. Esteky
  Status:   In Proceedings
  Proceeding: ECVP
  Year:  2002
  Supported by:  IPM
In the spatial-crowding effect, subjects are unable to report the orientation of the crowded target; however, they can estimate the average orientation by compulsory averaging of local orientation signals (Parkes et al, 2001 Nature Neuroscience 4 739 - 744). Distance dependence of this averaging was studied by two experiments. In the first experiment, subjects reported the orientation of a Gabor patch in the crowding condition in which distractors were arranged in a crossed array. Distractors whose orientation was similar to the target were presented near to or far from the target stimulus. In the second experiment, the eccentricity effect of similar distractors with the target was considered by locating the distractors in a radial array. The results showed that near similar distractors improve the performance more than far similar distractors (p < 0.0001). The best performance was obtained with distractors all similar to the target, which confirmed the averaging process for crowded signals. The results of the crowding experiment with the radial array demonstrated the pure effect of distance and significant interaction of eccentricity with distance (p < 0.01); however, there was no significant effect of eccentricity (p = 0.83). We conclude that improvement in performance through similarity between target and distractors is dependent on distance. So near similar distractors give more weight for the averaging process.

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