The effect of retinal location on the magnitude of the Poggendorff illusion

The effects of peripheral and central fixation on a Poggendorff-like vernier alignment task

“…Five groups of 10 subjects each completed these C and E judgments under one conditiort' of inspection. There were three major findings: (1) contrary to expectations arising from results' obtained by Novak (1966), there was no difference between the condition in which observers were instructed to fixate the point at which the oblique line abutted the inducing line and the condition in which free inspection was permitted; (2) contrary to a recent report by Greist and Grier (1977), alignment errors were not eliminated in conditions involving fixation directly above or below the point of abuttal; instead, effects similar to those reported by Prytulak (1973) occurred in both Conditions C and E, and these effects consequently were not significant in the corrected (E-e) difference measures; and (3) when alignment errors were converted to angular displacements, mean errors decreased linearly as a function of the distance between the tip of the oblique line and the response dot. This third finding was attributable to nonzero intercepts of error functions, and the result was considered in relation to the tenability of various hypotheses concerning the nature of abutting line effects.…”

“…In a recent investigation of the Poggendorff illusion Greist and Grier (1977) reported that peripheral fixation to the left or right of the stimulus had no effect on the magnitude of the illusion but that peripheral vertical fixation abolished the illusion entirely, whether the fixation point was 3.12°above or below the stimulus, the total size of which was about 1.25°. Earlier, Novak (1966) had found a significant reduction in the Poggendorff effect with central fixation, compared to the illusion which occurred under completely free inspection.…”

“…First, smaller but significant alignment errors, in the same direction as the Poggendorff effect, occur with such a parallelless Poggendorff figure (Curthoys, Wenderoth, & Harris, 1975;Day, 1973;Day & Dickinson, 1976;Wundt, 1886), and it is of interest to establish whether instructed fixation affects only this vernier alignment This research is part of a project (Grant No. A74/15177) supported by the Australian Research Grants Committee in 1975 and1977. Peripherals and software for the display were developed by Mike Cooper, Alan Parkinson, and John Holden, to whom we are grateful; Phil Greenwood and Margie Morgan assisted in collecting the data.…”

Visual field differences in the magnitude of the Oppel-Kundt illusion vary with processing time

“…field differences in the magnitudes of the Ponzo illusion (Bertelson & Morais, 1983), the Poggendorff illusion (Greist & Grier, 1977), and the rod-and-frame and tilt illusions (Magnussen, Landro, & Johnsen, 1985).…”

An investigation into perceived motion paths by means of the Slalom Illusion

“…Novak (1966) compared free-viewing conditions to controlled central fixation, and observed a significant reduction in the size of the Poggendorff illusion in the central fixation condition. Greist and Grier (1977) report that the Poggendorff illusion was unaffected by horizontal displacements, but it disappeared when the stimulus was vertically displaced from the centre of fixation. Wenderoth, White, and Beh (1978) however, could not replicate the latter effect, nor the finding of Novak (1966).…”