Component Analysis of Orientation Illusions

Abstract

Orientation illusions occur when the inducing figure is a line or grating (the tilt illusion) or a square outline frame (the rod-and-frame illusion). In the range of inducing figure tilts between vertical and horizontal, the tilt illusion describes one cycle of positive (direct) and negative (indirect) effects but the rod-and-frame illusion describes two such cycles. In two experiments, angular functions of illusions were measured with the six possible inducing figures which result when two of the four sides of a square inducing frame are deleted. As expected, the parallel-side frame amputations induced angular functions similar to the tilt illusion and these functions differed from those induced by the orthogonal-sided amputations. In agreement with previous findings on the nonadditivity of tilt illusions, the sum of angular functions induced by frame amputations, which together form a complete frame, were not always equivalent to the angular function induced by a complete frame, and there were asymmetries in the data fro which neither of two simple hypotheses could adequately account. The discussion focuses upon properties of inducing figures which psychophysical hypotheses might need to consider in order to account for the shapes of angular functions of orientation illusions and, in particular,a distinction is drawn between the global orientation of the inducing figure and the orientations of it (local) component features. It is suggested that it might be fruitful if the tilt illusion and the rod-and-frame illusion were conceived of as illusions resulting from inducing figures composed of all or part of n gratings of spatial frequency fn intersecting at angles of 180 degrees/n.

Strategic and perceptual factors producing tilt contrast in dot localization

“…Carpenter and Blakemore (1973) have proposed that tilt contrast is the result of lateral inhibition among orientation-specific cortical cells early in visual perception, but tilt contrast occurs betweentest lines and "virtual" axes of symmetry, such as the diagonal in Schiano and Tversky's stimuli (Hartley, 1982;Wenderoth & Curthoys, 1974;Wenderoth, Johnstone, & van der Zwan, 1989). Becausethe inhibition of local orientation cells could not explain this finding, Wenderoth and colleagues (Beh, Wenderoth, & Purcell, 1971;Wenderoth & Beh, 1977;Wenderoth et al, 1989) proposed the major axes hypothesis, which states that a line will appear tilted away from the nearest axis of mirror symmetry in the reference frame, including axes not actually present in the figure. In the orthogonal frame discussed here, axes of symmetry correspond to the physical horizontal and vertical axes and the virtual diagonal formed by those axes.…”

“…This pattern is also consistent with repulsion from the horizontal and vertical axes, but does not explain why the lines were not repulsed by the diagonal axis of mirror symmetry, as predicted by Wenderoth's major axes hypothesis (e.g., Wenderoth et aI., 1989), and observed in Schiano and Tversky's first two experiments. It is unclear why instructions to use the diagonal as a referent produces an attraction effect toward the diagonal, given that tilt contrast occurs between test lines and virtual axes of symmetry (Wenderoth & Beh, 1977;Wenderoth et al, 1989). Schiano and Tversky argue that the attraction to the diagonal is entirely a strategic effect, similar to cognitive landmark effects observed in more abstract distance estimation tasks (e.g., Rosch, 1975).…”

Structure and strategy in encoding simplified graphs

“…Recently, Wende roth and colleagues (Wenderoth, Johnstone, & van der Zwan, 1989; see also Wenderoth, 1977;Wenderoth & Beh, 1977) have proposed a new way of conceptualizing tilt effects, which may prove useful in interpreting the present data. Specifically, the~have argut hat many tilt distortions may be profitably Interpreted In terms of the major axes hypothesis, originally formulated as a general description of rod-and-frame phenomena.…”

Frame effects in visual search for line orientation

“…If the contrast effects induced distortion of the perceived orientation of the inside line in the search task, the TBC should change the search performance from that obtained in the NF condition. In the literature on RF effects, frames consisting of only a pair of parallel lines were found to induce a distortion of the apparent vertical of the rod (Wenderoth & Beh, 1977).…”

“…As compared with those for large surrounding frames, the results for an LF would be more easily related to RF effects in relevant conditions. In some of the present experiments, we manipulated the physical properties of the LF, as has been done in studies of RF effects (Streibel, Barnes, Julness, & Ebenholtz, 1980;Wenderoth & Beh, 1977).…”