The Poggendorff Illusion: An Illusion of Linear Extent?

Perception ◽  
1981 ◽  
Vol 10 (2) ◽  
pp. 155-164 ◽  
Author(s):  
Suzanne Greist-Bousquet ◽  
Harvey R Schiffman
Keyword(s):  
Poggendorff Illusion ◽  
Acute Angle ◽  
Obtuse Angle ◽  
Spatial Distortion ◽  
Standard Version ◽  
Lyer Illusion ◽  
Poggendorff Figure ◽  
Linear Extent ◽  
Poggendorff Effect ◽  
Intersection Points

In the standard version of the Poggendorff figure a transversal intersects two parallel verticals and the segment of the transversal between the two intersection points, A and B, is not shown. The two portions of the transversal outside the parallels then seem to be misaligned. Besides this illusion of direction, there is also an illusion of size, the distance AB being underestimated in the standard figure. The influence of configural components in determining this spatial distortion of the Poggendorff figure was examined by having subjects reproduce the inner oblique (at 45°) extent AB in variations of the figure. This distance was found to be underestimated in Poggendorff variations which contained parallel (vertical) components that formed an acute angle with AB; and the underestimation increased as the number of these components present in the figure increased. The distance AB was found not to be significantly distorted in figures which contained only those parallel (vertical) components that formed an obtuse angle with AB, yet their presence in the figure tended to counteract the underestimation. When the transversals were omitted, the underestimation was found to increase. The findings are interpreted in support of an explanation that reduces the Poggendorff effect to those factors which mediate the Müller-Lyer illusion.

Are the Obtuse Angles the Key Components of the Poggendorff Illusion?

Perception ◽  
1981 ◽  
Vol 10 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Peter Wenderoth ◽  
Michael Johnson
Keyword(s):  
Poggendorff Illusion ◽  
Acute Angle ◽  
Obtuse Angle ◽  
Negative Effects ◽  
Linear Summation ◽  
Displacement Effect ◽  
Positive Effects ◽  
Poggendorff Figure

An experiment is reported which confirms and extends a previous finding that amputations of the Poggendorff figure do not necessarily result in large positive effects with obtuse-angle stimuli, and small or even negative effects with acute-angle stimuli. Indeed, the acute-angle effects found were significantly greater than the obtuse-angle effects, and the full Poggendorff error was not explicable in terms of the linear summation of the component-angle effects. An ‘alignment displacement effect’ reported earlier by Hotopf and Obonai was shown to occur, but could not be an important component of the Poggendorff illusion.

Endothelial nitric oxide synthase (eNOS) mediates neointimal thickness in arteriovenous fistulae with different anastomotic angles in rats

2021 ◽  
pp. 112972982199653
Author(s):  
Hualong Bai ◽  
Shunbo Wei ◽  
Boao Xie ◽  
Zhiwei Wang ◽  
Mingxing Li ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Endothelial Nitric Oxide Synthase ◽  
Neointimal Hyperplasia ◽  
Acute Angle ◽  
Obtuse Angle ◽  
Enos Expression ◽  
Arteriovenous Fistulae ◽  
Neointimal Thickness ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

Background: It is known that the anastomotic angle can influence neointimal hyperplasia and patency in arteriovenous fistulae (AVF). Endothelial nitric oxide synthase (eNOS) is released from the vascular endothelium and can inhibit neointimal hyperplasia. Therefore, here, we aimed to test the hypothesis that the manipulation of eNOS expression could influence neointimal thickness in a rat AVF model with different anastomosis angles. Methods: Rat carotid artery (inflow, CA) and jugular vein (outflow, JV) AVF were created with acute, blunt, or end-to-end (ETE) anastomosis angles. Aspirin was used to increase eNOS expression in the acute angle group, while N(G)-nitro-L-arginine methyl ester (L-name) was used to decrease eNOS expression in the obtuse angle group. The rats were sacrificed on day 21, and tissues were harvested and analyzed histologically and with immunostaining. Results: A larger anastomosis diameter ( p < 0.016) and smaller neointimal area ( p < 0.01) were observed in the obtuse and end-to-end (ETE) groups compared to in the acute group. In the acute angle group, there were more proliferating cell nuclear antigen (PCNA) and α-actin dual-positive cells ( p < 0.0001) and fewer phospho (p)-eNOS-positive endothelial cells ( p < 0.0001) in the neointima than in the obtuse and ETE angle groups. On treating the acute angle and blunt angle groups with aspirin and L-name, respectively, no significant differences in the neointima/lumen rate were observed ( p = 0.6526) between the groups; however, there were fewer von Willebrand factor (vWF) and p-eNOS dual-positive cells in the obtuse angle group treated with L-name ( p = 0.0045). Conclusions: We demonstrated that eNOS plays an important role in neointimal hyperplasia in AVF with different anastomosis angles; further, eNOS could potentially be used as a therapeutic target in patients with AVF in the future.

scholarly journals Rhombus and Rhomboid Parallelogram Patterns on Glaciers: Natural Indicators of Strain

1979 ◽  
Vol 22 (87) ◽  
pp. 247-261 ◽  
Author(s):  
Charles J. Waag ◽  
Keith Echelmeyer
Keyword(s):  
Strain Rate ◽  
Flow Direction ◽  
Acute Angle ◽  
Principal Strain ◽  
Obtuse Angle ◽  
Strain Rates ◽  
Ice Flow ◽  
Glacier System ◽  
Glacier Ice

AbstractSubtle rhombus and rhomboid parallelogram patterns occur on Vaughan Lewis Glacier and the Gilkey Glacier System, Juneau Icefield, Alaska. The patterns are within the firn at the firn-ice interface, are formed by differential recrystallization within narrow preferred zones, and are apparently manifestations of stresses transferred upward from the glacier ice. On the glaciers of the Gilkey System the patterns occur where intense lateral shortening is indicated by abrupt convergence of medial moraines and an abundance of extension crevasses. The short axes of the rhombi and the obtuse angle bisectors of the rhomboids are subparallel to the strike of extension crevasses, therefore to the axis of shortening. The long axes of the rhombi and the acute angle bisectors of the rhomboids are parallel to the foliation, and ice-flow direction. The angles of the parallelograms are variable locally, but average 105° and 75°; the variation seems to reflect intensity and duration of stress. Similar parallelograms occur within the troughs of wave bulges below the Vaughan Lewis Icefall. In the wave bulges, the foliation arcs parallel the wave. The long axes of the rhombi and acute angle bisectors of the rhomboids parallel the foliation around the foliation arc. The short axes of the rhombi and the obtuse angle bisectors of the rhomboids parallel the strikes of radial crevasses, are perpendicular to the direction of extension, and form a fan divergent down-stream. The precise mechanisms and conditions of formation of the parallelograms are not yet understood. Preliminary strain-rate measurements suggest, however, that correlations exist between the orientations of the principal strain-rates and the axes of the patterns, and between the magnitude of the strain-rates and the axial lengths of the patterns.

scholarly journals The Haptic Müller-Lyer Illusion in Sighted and Blind People

Perception ◽  
10.1068/p3340 ◽  
2002 ◽  
Vol 31 (10) ◽  
pp. 1263-1274 ◽  
Author(s):  
Morton A Heller ◽  
Deneen D Brackett ◽  
Kathy Wilson ◽  
Keiko Yoneyama ◽  
Amanda Boyer ◽  
...  
Keyword(s):  
Visual Imagery ◽  
Visual Experience ◽  
Low Vision ◽  
Blind People ◽  
Spatial Distortion ◽  
Lyer Illusion ◽  
Visual Status ◽  
Nonsignificant Difference ◽  
Congenitally Blind ◽  
Size Estimates

We examined the effect of visual experience on the haptic Müller-Lyer illusion. Subjects made size estimates of raised lines by using a sliding haptic ruler. Independent groups of blindfolded-sighted, late-blind, congenitally blind, and low-vision subjects judged the sizes of wings-in and wings-out stimuli, plain lines, and lines with short vertical ends. An illusion was found, since the wings-in stimuli were judged as shorter than the wings-out patterns and all of the other stimuli. Subjects generally underestimated the lengths of lines. In a second experiment we found a nonsignificant difference between length judgments of raised lines as opposed to smooth wooden dowels. The strength of the haptic illusion depends upon the angles of the wings, with a much stronger illusion for more acute angles. The effect of visual status was nonsignificant, suggesting that spatial distortion in the haptic Müller-Lyer illusion does not depend upon visual imagery or visual experience.

The Poggendorff Illusion and Apparent Interparallel Extents

Perception ◽  
1992 ◽  
Vol 21 (5) ◽  
pp. 599-610 ◽  
Author(s):  
Ross H Day ◽  
Erica J Stecher ◽  
Andrea L Parker
Keyword(s):  
Poggendorff Illusion ◽  
Parallel Line ◽  
Significant Error ◽  
The Other ◽  
Misalignment Effect ◽  
The Third ◽  
Horizontal Extent ◽  
Lyer Illusion

An explanation of the Poggendorff misalignment effect in terms of apparent contraction of interparallel extent resulting from the Müller-Lyer illusion was tested in three experiments. Three of the eight stimulus figures had oblique transversals outside the parallels in the usual way, three had them inside, and two were controls consisting of the transversals only. Müller-Lyer forms were differently delineated between the parallels for the inside-transversal and outside-transversal figures, and were not delineated in the control figures. In the first experiment apparent misalignment occurred in four of the six parallel-line figures and in neither of the controls. In the second experiment oblique extent between the parallels was underestimated in six of the eight figures and right-angle extent was overestimated in all of them. The results of the third experiment showed that right-angle (horizontal) extent between the parallels without transversals is estimated without significant error. The data from the three experiments do not support the interparallel-extent explanation of apparent misalignment. Instead, the results are interpreted in terms of independent perceptual compromises, one involving alignment of the transversals and the other the distance between them.

Geometric-Optical Illusions Under Isoluminance?

2017 ◽  
Author(s):  
Kai Hamburger ◽  
Thorsten Hansen ◽  
Karl R. Gegenfurtner
Keyword(s):  
Poggendorff Illusion ◽  
Ponzo Illusion ◽  
Ebbinghaus Illusion ◽  
Optical Illusions ◽  
Magnocellular System ◽  
Lyer Illusion ◽  
System P ◽  
Visual Areas ◽  
Parvocellular System ◽  
Delboeuf Illusion

This chapter briefly introduces nine classical geometric-optical illusions. These include the Delboeuf illusion, the Ebbinghaus illusion, the Judd illusion, the Müller-Lyer illusion, the Ponzo illusion, the vertical illusion, the Hering illusion, the Poggendorff illusion, and the Zoellner illusion. It then demonstrates that they persist under different luminance conditions and under isoluminance. The empirical findings show that our conscious percept is similarly affected by luminance conditions and isoluminance, suggesting that joint contour processing (chromatic and luminance) may extend well beyond early visual areas. The chapter further discusses these concepts in terms of the magnocellular system, the parvocellular system, and the koniocellular system.

scholarly journals The hexahydrated double selenates containing thallium. Completion of the thallium salts and of the whole monoclinic series

1928 ◽  
Vol 118 (780) ◽  
pp. 393-426 ◽  
Keyword(s):  
Ferrous Iron ◽  
Preceding Paper ◽  
Acute Angle ◽  
Obtuse Angle ◽  
Density Measurements ◽  
Cobalt Nickel ◽  
Nickel Cobalt ◽  
Volume Properties ◽  
Iron Nickel ◽  
First Time

The introduction to the preceding memoir (p. 367) applies equally to this paper, in which are described the six double selenates containing thallium as the R-metal and magnesium, ferrous iron, nickel, cobalt, manganese, and copper as the M-metal respectively. The optical and volume properties and constants of the zinc-thallium selenate are also included, as these were not determinable with the crystals described in 1909, while lately the author has obtained quite excellent crystals of this salt suitable for all purposes. While this work has been in progress a paper by L. C. Lindsley and L. M. Dennis has appeared, concerning five of these thallium double selenates, those in which the M-metal is copper, cobalt, nickel, magnesium, and manganese, which they consider to have made for the first time. This is, of course, an error, as all of them were made by the author previous to 1909, as will be clear from p. 367 of the preceding paper; but, as there stated, the crystals obtained were not of adequate perfection for complete goniometrical, optical and density measurements and determinations. Lindsley and Dennis, however, only give measurements of two angles, and these are supplementary to each other, being the acute and obtuse angles of the primary prism p {110}. They give no optical or other physical data. They found in the case of each salt an increase of about 40' in the acute angle of the prism, and a like amount of diminution of the supplementary obtuse angle, compared with the corresponding angle on the crystals of the analogous double sulphate.

Acute Angles and the Poggendorff Illusion

1972 ◽  
Vol 24 (2) ◽  
pp. 169-174 ◽  
Author(s):  
A. W. Pressey ◽  
O. Sweeney
Keyword(s):  
Poggendorff Illusion ◽  
Test Line ◽  
Acute Angle ◽  
Highly Effective ◽  
Formed Part ◽  
Apparent Orientation

Burns and Pritchard's (1971) explanation of the Poggendorff illusion is criticized. An experiment was designed to determine whether the acute angle plays any role in the perception of the illusion. The results showed that (i) an inducing line which crossed a test-line was highly effective in altering the apparent orientation of the test line, (ii) an inducing line forming an acute angle with a test-line had a small effect in changing the apparent orientation of the test-line, and (iii) an acute angle which formed part of the Poggendorff configuration produced an effect opposite to that predicted by the view that acute angles are perceptually enlarged.

The Oblique Line Illusion: The Poggendorff Effect without Parallels

1973 ◽  
Vol 25 (4) ◽  
pp. 535-541 ◽  
Author(s):  
R. H. Day
Keyword(s):  
Oblique Line ◽  
Median Plane ◽  
Poggendorff Figure ◽  
Poggendorff Effect

The apparent misalignment of two oblique collinear lines was investigated in two experiments. In the first the effect with the lines at 45° to the median plane was compared with that for the same two lines separated by the conventional parallels of the Poggendorff figure. The illusion with the two lines was consistent and significant but about one-third the magnitude of that with the parallels. The two illusions were significantly correlated. In the second experiment the angle of the two oblique, collinear lines was varied in 15° steps. The misalignment illusion was maximal at 45° and smaller but significant at 60 and 75°. There was no significant effect at 15 and 30°.

scholarly journals The relation between apparent extent and alignment in the Poggendorff illusion: A response to “No evidence for apparent extent between parallels as the basis of the Poggendorff effect,” by Day, Jolly, and Duffy

1989 ◽  
Vol 46 (5) ◽  
pp. 501-504 ◽  
Author(s):  
Suzanne Greist-Bousquet ◽  
H. R. Schiffman ◽  
Richard Dorsett ◽  
Janet Davis
Keyword(s):  
Poggendorff Illusion ◽  
Poggendorff Effect
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