scholarly journals Evidence for a significant contribution of interactions between oriented line segments in the Tolansky version of the Poggendorff illusion

1986 ◽  
Vol 39 (5) ◽  
pp. 334-338 ◽  
Author(s):  
Peter Wenderoth ◽  
Tony O’Connor ◽  
Michael Johnson
Keyword(s):  
Poggendorff Illusion ◽  
Significant Contribution ◽  
Line Segments ◽  
Oriented Line

Poggendorff Illusion as a Function of Orientation of Transversal and Parallel Lines

1976 ◽  
Vol 43 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Barry S. Anton
Keyword(s):  
Visual Acuity ◽  
Line Segment ◽  
Poggendorff Illusion ◽  
Human Subjects ◽  
Parallel Line ◽  
Normal Vision ◽  
Transversal Line ◽  
Line Segments ◽  
Adult Human ◽  
Parallel Lines

Adult human subjects (8 male, 8 female undergraduates) with normal vision were required to judge various orientations of the Poggendorff illusion. The transversal and parallel line-segments of the illusion were manipulated to produce the orientations to be judged. Minimum illusion occurred when the transversal line-segment was oriented 90° with respect to true vertical or true horizontal. Magnitude of illusion increased as the transversal line-segment deviated from these positions. The findings suggested that there is a stability of horizontal and vertical orientations. In addition, the hypothesis that visual acuity plays a role in the perception of the Poggendorff illusion was proposed.

Rational Bézier and B-Spline Ruled Surface Patches

1996 ◽  
Author(s):  
Q. J. Ge ◽  
Donglai Kang
Keyword(s):  
Ruled Surfaces ◽  
Dual Numbers ◽  
Line Segments ◽  
B Spline ◽  
Surface Patches ◽  
Spline Curves ◽  
Oriented Line ◽  
Euclidean Three Space ◽  
Three Space ◽  
Projective Algorithms

Abstract This paper presents a geometric method for constructing bounded rational Bézier and B-spline ruled surfaces directly from line-segments. Oriented line-segments in a Euclidean three-space are represented by vectors with four homogeneous components over the ring of dual numbers. Projective algorithms for rational Bézier and B-spline curves are dualized to yield algorithms for rational Bézier and B-spline ruled surfaces.

scholarly journals Flashed Müller-Lyer and Poggendorff Virtual Illusions

i-Perception ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 204166952110156
Author(s):  
Stuart Anstis ◽  
Patrick Cavanagh
Keyword(s):  
Poggendorff Illusion ◽  
Moving Frame ◽  
Illusory Effect ◽  
Line Segments ◽  
Lyer Illusion ◽  
Before And After ◽  
Position Shift ◽  
Initial Arrangement

A moving frame can dramatically displace the perceived location of stimuli flashed before and after the motion. Here, we use a moving frame to rearrange flashed elements into the form of classic illusions. Without the moving frame, the initial arrangement of the flashed elements has no illusory effect. The question is whether the frame-induced displacement of position precedes or follows the processes underlying the illusions. This illusory offset of flashed chevrons does generate a Müller-Lyer illusion and the illusory offset of two line segments does create a Poggendorff illusion. We conclude that the site where the frame-induced position shift emerges must precede the site at which the Müller-Lyer and Poggendorf illusions arise.

Collinearity Judgment as a Function of Induction Angle

1994 ◽  
Vol 78 (2) ◽  
pp. 655-674 ◽  
Author(s):  
Ernest Greene
Keyword(s):  
Line Segment ◽  
Poggendorff Illusion ◽  
Orientation Selectivity ◽  
Induction Effect ◽  
Neural Models ◽  
Line Segments ◽  
Tilt Illusion ◽  
Test Segment ◽  
Segment Orientation ◽  
Basic Induction

The misalignment which is seen in the Poggendorff illusion can be studied with better control by using a configuration which has only two line segments. Two experiments were conducted in which subjects judged collinearity of a test segment, this judgment being subjected to a biasing influence from a second (induction) segment. Exp. 1 held the test segment at one of three orientations relative to the observer (30°, 45°, and 60°) and systematically varied the orientation of the induction segment in 15° increments through the range of possible positions. The orientation of the page relative to the observer was varied as well. Exp. 2 varied the test segment through a greater range of angles and sampled more levels of induction segment orientation. Analysis indicated that projection errors follow orderly rules similar in kind to but different in magnitude from those observed for the Tilt Illusion, most notably, (a) misprojection is greatest when the orientation of the interfering line is similar to that of the line segment being projected and (b) the strength of this influence decreases as the relative angle becomes orthogonal. Also, the orientation of the segment being projected relative to the observer serves to modulate the strength of the basic induction effect. These perceptual interactions are discussed in relation to neural models for orientation selectivity.

Anisotropy in Oriented-Line-Target Detection at High and Low Luminance Contrast

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 38-38 ◽  
Author(s):  
L M Doherty ◽  
D H Foster
Keyword(s):  
Target Detection ◽  
Line Segment ◽  
Visual Angle ◽  
Detection Threshold ◽  
Luminance Contrast ◽  
High Luminance ◽  
Line Segments ◽  
Low Luminance ◽  
Line Target ◽  
Oriented Line

Observers can detect a uniquely oriented line segment (‘target’) in a background field of uniformly oriented line segments (‘nontargets’) even if viewing time is brief. When the lines have high luminance contrast, the variation of orientation increment threshold with nontarget orientation is periodic, generally with a period of about 90° although smaller periods have been found. Do the orientation-sensitive mechanisms giving rise to periodicities function only at high contrast? This question was addressed in a line-target detection experiment. Twenty white line segments of length 1 deg visual angle were presented in a circular field of diameter 20 deg visual angle. Nontarget orientations were in the range 0°, 5°, …, 175°, and the difference between nontarget and target orientations was varied adaptively. Stimulus displays lasting 40 ms were followed by a blank interstimulus interval lasting 60 ms and then a random-line mask. A view-tunnel provided a grey background of luminance 35 cd m−2 and stimulus contrast was 0.1, 0.3, 0.5, 0.7, or 0.9 log unit above the observer's luminance detection threshold for one line segment. When contrast was 0.1 log unit above this threshold, performance was near chance level. As contrast increased from 0.3 to 0.9 log unit above luminance detection threshold, performance improved and orientation increment thresholds decreased, showing that early orientation-processing is most effective at high luminance contrast. Nonetheless, periodicities were found in all conditions where performance was better than chance which suggests that the orientation-sensitive mechanisms associated with periodicities operate at both high and low luminance contrast.

The Corner Poggendorff

Perception ◽  
1988 ◽  
Vol 17 (1) ◽  
pp. 65-70 ◽  
Author(s):  
Ernest Greene
Keyword(s):  
Relative Position ◽  
Poggendorff Illusion ◽  
Oblique Line ◽  
The Other ◽  
Line Segments ◽  
Poggendorff Effect

With the classic Poggendorff illusion a set of parallel ‘induction lines’ will cause a set of oblique line segments to look misaligned even though they are collinear. A different kind of misalignment can be produced by placing the induction lines so that they form a corner. Under these conditions the obliques will appear to be angled slightly, one relative to the other. The effects are small, but can be seen and reliably reported by a group of naive subjects. The influence of the induction lines drops sharply as their relative position is moved from parallel to orthogonal, but there is a small residual influence which may be called the corner Poggendorff effect.

Stabilizing pyritic material

1989 ◽  
Vol 4 ◽  
pp. 244-248 ◽  
Author(s):  
Donald L. Wolberg
Keyword(s):  
Significant Contribution ◽  
Organic Materials ◽  
Sedimentary Rocks ◽  
Iron Sulfides ◽  
Decomposition Products ◽  
Iron Minerals ◽  
Pyrite Formation ◽  
Organic Sediments ◽  
Freshwater Environments

The minerals pyrite and marcasite (broadly termed pyritic minerals) are iron sulfides that are common if not ubiquitous in sedimentary rocks, especially in association with organic materials (Berner, 1970). In most marine sedimentary associations, pyrite and marcasite are associated with organic sediments rich in dissolved sulfate and iron minerals. Because of the rapid consumption of sulfate in freshwater environments, however, pyrite formation is more restricted in nonmarine sediments (Berner, 1983). The origin of the sulfur in nonmarine environments must lie within pre-existing rocks or volcanic detritus; a relatively small, but significant contribution may derive from plant and animal decomposition products.

Discrimination of Occluded Line Segments by Pigeons

2009 ◽  
Author(s):  
Robert G. Cook ◽  
Carl Erick Hagmann
Keyword(s):  
Line Segments
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