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M. Brodeur, F. Lepore, B. Debruille; Simultaneity in the Presentation of Separated Parts of an Incomplete Shape Facilitates Their Binding . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4116.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Illusory contours and binding of contours have frequently been studied with the presentation of Kanizsa-like figure. This illusory figure includes an incomplete shape of similar brightness and color to the background. The visible parts of the contour are defined by the contrast between the angles of the shape and "pacmen"-like forms called the inducers. In the modal version of this figure, illusory contours complete the sides of the shape in the gaps separating the visible angles leading to the impression that the shape overlays partially the inducers. In the amodal version, the indentations are closed by a line, giving the impression that the shape is placed behind the inducers (as if the inducers were holes). To control for the binding, inducers are simply rotated outward so as to disrupt the alignment of the angles. The N1, a component of the visual evoked potentials associated to the binding, is always larger for the modal figure relative to the amodal and the control figures probably because it includes more binding cues (i.e. elements that facilitate the binding) such as the alignment and the belonging of the angles. However, the simultaneity in the presentation of the angles has never been used as a cue for the binding of illusory figures. Methods: In the present experiment, subjects had to decide of the presence and the absence of a square in 60 modal, 60 amodal squares, and 60 controls of each version of the figures. Figures were presented for 600ms at an interval of 5s. Fourteen subjects performed the experiment twice but in one version (experiment B), four full disks of similar dimension to the inducers are permanently presented throughout the experiment so that the figure appeared following the simultaneous apparition of the angles over the circles. In the other experiment (experiment A), there was no simultaneity cues as the inducers appear along the angles. Results: The modal figure evoked the largest N1 in the experiment A but the smallest in the experiment B because the N1 of all figures, except that of the modal one, got strongly enhanced in the experiment B relative to the experiment A. Conclusions: This effect showed that figures lacking cues of binding benefit more of the simultaneity presentation of their parts than figure easily bound by other cues.
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