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Haluk Ogmen, Michael H. Herzog; Spatio-temporal integration in grouping-based feature attribution. Journal of Vision 2005;5(8):960. doi: 10.1167/5.8.960.
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© ARVO (1962-2015); The Authors (2016-present)
By using a Ternus-Pikler display, we showed that features presented at one spatial location can be perceived at another one, in violation of retinotopic relations but in accordance with perceptual grouping (Herzog & Ogmen, VSS'05). Here, we extend these results by showing that features of elements presented at two distinct retinotopic loci can be combined. The stimulus consisted of a first frame (70ms) containing three vertical lines, an ISI (100ms), and a second frame (70ms) containing three lines shifted to the right. The second and third line of the first frame overlapped spatially with the first and second line of the second frame, respectively. With this set-up, group motion is perceived: the lines of the first frame are mapped onto corresponding lines of the second frame.We inserted a vernier offset to the central element of the first frame. An additional vernier offset of opposite direction was inserted to one of the remaining elements in the first or the second frame. Observers' task was to report the perceived direction of vernier offset (left of right) for a pre-designated line in the second frame. Naïve observers had no knowledge where vernier offsets were presented. Our results show that the integration of the vernier information across the two frames follows the rules of motion grouping; e.g. a vernier offset of the second element of the first frame is integrated with the vernier offset of the second element of the second frame- even though these elements reside at different spatial locations. The close relationship that we show between perceptual grouping and feature attribution suggests that the visual system violates retinotopic relations in order to maintain spatio-temporal contiguity of object identities in the perceptual space.
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