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Hoko Nakada, Ikuya Murakami; Interactions between different visual features in the ensemble perception of size. Journal of Vision 2020;20(11):983. doi: https://doi.org/10.1167/jov.20.11.983.
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© ARVO (1962-2015); The Authors (2016-present)
It is widely known that the visual system is able to extract summary statistics from a group of multiple objects sharing a certain visual feature. Although a lot of studies have examined various kinds of ensemble perception, such as average size, hue, motion direction and speed, it remains to be clarified how these summary statistics are calculated within a single feature or across different features. Here, we focused on the average size of an array of circles, which is known to be perceived accurately even for very brief displays, and investigated whether the perceived average size of circles having a particular distinct feature was affected by the average size of distractors, namely circles having another distinct feature. Observers were presented with an array of blue circles arranged on the left and right sides of the display and made a two-alternative forced-choice judgment about which side contained blue circles with the larger average size. Each side also contained an array of green circles with one of three average sizes. Parameters were set so that shifts in psychometric functions should mean that the average size of the ignored green circles affected the perceived average size of the blue circles. We also did another experiment by exchanging the roles of these two colors, namely green to be focused on and blue to be ignored. The results showed asymmetry between blue and green. Averaging of blue circles was not affected by green distractors, whereas averaging of green circles was affected by blue distractors, such that an array of green circles accompanied by blue distractors with a larger average size was judged as having a larger average size. These results indicate compulsive contribution from distractors in rapid ensemble perception of size and suggest that the perceptual distinctiveness of color plays a key role.
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