Geometrical features underlying the perception of collinearity.
The magnitude of the Poggendorff bias in perceived collinearity was measured with a 2AFC task and roving pedestal, and was found to be in the region of 6-8deg, within the range of previous estimates. Further measurements dissected the bias into several components: (1) The small (∼1deg) repulsion of the orientation of the pointer from the parallel, probably localized in the part of the line near the intersection (2) A small (<1deg) location bias affecting the intersection of pointers and inducing lines; and (3) A larger (>1deg) bias in the orientation of virtual lines crossing the gap between two parallels, towards the orientation of the parallels, or equivalently (4) An orthogonal bias in actively constructing a virtual line across the gap. We conclude that orientation repulsion by itself is an inadequate explanation of the Poggendorff effect, and that a full explanation must take account of the way in which observers construct virtual lines in visual space in order to carry out elementary geometrical tasks such as extrapolation.
Max-Planck Institute for Metabolism Research, Cologne, Germany; Division of Optometry and Visual Science, Institute of Health Sciences, City University London, United Kingdom. Electronic address: Michael.Morgan@sf.mpg.de.
Michael
M
Morgan
Max-Planck Institute for Metabolism Research, Cologne, Germany.
Barbara
B
Dillenburger
D000328:Adult; D004193:Discrimination Learning; D004215:Distance Perception; D005260:Female; D006801:Humans; D008297:Male; D009903:Optical Illusions; D009949:Orientation; D010364:Pattern Recognition, Visual; D013028:Space Perception
Alignment acuity; Poggendorff; Spatial vision