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Topic: Poggendorf Illusion

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	Optical illusion - Wikipedia, the free encyclopedia
		An optical illusion is a type of illusion characterized by visually perceived images that are deceptive or misleading [1].
		There are physiological illusions, that occur naturally, and cognitive illusions, that can be demonstrated by specific visual tricks that show particular assumptions in the human perceptual system [2].
		Fiction illusions are the perception of objects that are genuinely not there to all but a single observer, such as those induced by schizophrenia or hallucinogenic drugs.
	en.wikipedia.org /wiki/Optical_illusion (658 words)

	Optical illusion - the free encyclopedia (Site not responding. Last check: 2007-10-09)
		An optical illusion is any illusion that deceives the human visual system into perceivingsomething that is not present or incorrectly perceiving what is present.
		Paradox illusions offer objects that are paradoxical or impossible, such as the Penrose triangle or impossible staircasesseen, for example, in the work of M.
		Fiction illusions are the perception of objects that are genuinely not there to all but a single observer, such as thoseinduced by schizophrenia or hallucinogenic drugs.
	www.free-web-encyclopedia.com /?t=Oi (526 words)

	Psychology 132 - Poggendorf Illusion
		Illusions are thought by some to give special insight into how perceptual processing usually works.
		Suppose that your perception is your visual system's best guess as to what the physical world really is. Then the illusion may unveil what kind of inference the brain makes and what properties of the stimulus made the brain guess the way it did.
		This theoretical perspective on perception and on illusions is called a mediational approach, and assumes that some kind of cognitive processing (here, unconscious reasoning or an unconscious inference) must mediate between the physical stimulus and the perception of that stimulus.
	psychlops.psy.uconn.edu /psych132/manual/poggendorf.html (632 words)

	ipedia.com: Optical illusion Article (Site not responding. Last check: 2007-10-09)
		Optical illusions can occur naturally or be demonstrated by specific visual tricks that show particular assumptions in the human perceptual system.
		A mirage is an example of a natural illusion that is an optical phenomenon.
		Physiological illusions, such as the afterimages following bright lights or adapting stimuli of prolonged alternating patterns (contingent perceptual aftereffect, CAE), are the effects on the eyes or brain of prolonged stimulation of a specific type - brightness, tilt, colour, movement, and so on.
	www.ipedia.com /optical_illusion.html (582 words)

	Do people get better at the Poggendorf illusion? (Site not responding. Last check: 2007-10-09)
		The "Poggendorf Illusion" was first demonstrated by Johann C. Poggendorf, an editor of a Physics and Chemistry journal, in 1860.
		The "Poggendorf Illusion" Illusion" is actually based on another famous illusion known as the Zoellner illusion, which relies on the angle of the tilt between a test line and an oblique line in fabric patterns.
		The Poggendorf Illusion, which was first demonstrated by Johann C. Poggendorf in 1860, is still one of the most well known visual illusions.
	www.mercer.edu /camps/message/summer2000/summer2000-poggendorf.htm (464 words)

	Illusions Exhibits 1-27
		All of the illusions in the Adjust and Measure series demonstrate that perception is a creative process and the result of a myriad of assumptions that the brain makes when interpreting visual data.
		The vase and face illusion is an example of an image where the figure and ground can be reversed, however, it is not possible to see both the vases and faces (figure and ground) at the same time.
		These types of illusions are also referred to as 'ambiguous' or 'unstable' because they can correctly be interpreted in different ways and can appear to switch from one tothe other.
	www.questacon.edu.au /html/illusions_exhibits_1-27.htm (3825 words)

	Professor Richard Gregory on-line (Site not responding. Last check: 2007-10-09)
		We would have liked to obtain accurate measures of such things beloved by the experimental psychologist as the visual Constancies, but this was not practicable, for he tired easily, and we were anxious not to upset either him or the hospital staff.
		The lack of explanation of these illusions did not worry us greatly, for with more knowledge, which is bound to come with further research in perception, they will surely be explained, and then any findings should be relatable to general perceptual issues [ Footnote 10.
		The extent of the illusion as measured for S.B. is unusually small, though some "normal" observers can be found with a similar degree of illusion.
	www.richardgregory.org /papers/recovery_blind/3-observations_p2.htm (2662 words)

	Spatial Illusions, Alain Domercq (Site not responding. Last check: 2007-10-09)
		A spatial illusion is said to occur when the perceived model differs from the physical model whether in dimension, orientation, curvature or direction.
		More seriously, spatial illusions remain scientifically unexplained and researchers interested in vision are convinced that vision in man will not be explained until we understand why and how we see spatial illusions.
		For the amateur, it is also at his or her level a source of interrogation, but the prospect of embellishing his or her home-page might weight higher in some cases.
	www.cim.mcgill.ca /~image529/TA529/Image529_99/projects97/44_Domercq/Illusion.html (1005 words)

	Poggendorff Illusion (Site not responding. Last check: 2007-10-09)
		This illusion was discovered in 1860 by physicist and scholar JC Poggendorff, editor of Annalen der Physik und Chemie, after receiving a letter from astronomer F. Zöllner.
		In his letter, Zöllner described an illusion he noticed on a fabric design in which parallel lines intersected by a pattern of short diagonal lines appear to diverge (Zöllner’s illusion).
		Whilst pondering this illusion, Poggendorff noticed and described another illusion resulting from the apparent misalignment of a diagonal line; an illusion which today bears his name.
	www.michaelbach.de /ot/ang_poggendorff (236 words)

	[No title]
		Several well-known "geometric-optical illusions" are to be accounted for by the formative effect of the R-factor.
		This is due to the intersections of the straight lines with the bundle of ray-like lines; an arc (exaggerated in B) tends to intersect the rays in angles that are more "perpendicular" than the objective angles.
		It is odd that, given such a dramatic distortion of the actual metric relationships, one speaks of the "perspective" of a drawing rather than of the "illusion".
	www.enane.de /geomopt.htm (1169 words)

	IPL - Poggendorff description (Site not responding. Last check: 2007-10-09)
		The Poggendorff illusion is a misalignment effect produced by the interaction of diagonal line elements with horizontal and vertical edges.
		The strength of the illusion above is reduced by showing the rectangle lying in the same plane as the diagonal line or by aligning the diagonal with imaginary lines converging at a vanishing point.
		This kind of illusion can also lead to distortions in the reading of graphs; although the vertical distance between the two lines above is always the same, the slanted sections look closer in value than the straighter sections.
	www.ipsych.com /vis/poggendorff/poggend_desc.html (541 words)

	Illusions Activity 6
		They are all examples of Poggendorf's illusion, which was discovered over 100 years ago and has been studied and theorized about many times but never fully understood.
		These size, shape and direction distortions are very common illusions and occur as easily with any shape or combination, which offers a great opportunity to get students to develop their own misleading designs.
		This illusion is an example of the irradiation effect in which light colours appear larger than dark objects of the same size.
	www.questacon.edu.au /html/tg_p20.htm (1656 words)

	Global cues affect the apparent misalignment in the Poggendorf illusion (Site not responding. Last check: 2007-10-09)
		Global cues affect the apparent misalignment in the Poggendorf illusion
		NICI > Publications > 2003 > Global cues affect the apparent misalignment in the Poggendorf illusion
		Koning, A.R., and Van Lier, R.J. Global cues affect the apparent misalignment in the Poggendorf illusion.
	www.nici.kun.nl /Publications/2003/17192.html (42 words)

	The Principles of Artistic Illusions
		The illusion can be enhanced by adding recognizable figures, as in the version at the right is © 2001 by John C. Holden.
		This is an illusion of relative dimensions within a picture, which is a distortion of shape.
		The Poggendorf illusion, or `crossed bar' illusion invites us to judge which line, A or B, is aligned exactly with C. A good ruler can be used on the printed copy to check your answer.
	www.lhup.edu /~dsimanek/3d/illus1.htm (3200 words)

	Poggendorf Illusion - Encyclopedia Glossary Meaning Explanation Poggendorf Illusion (Site not responding. Last check: 2007-10-09)
		Poggendorf Illusion - Encyclopedia Glossary Meaning Explanation Poggendorf Illusion.
		The Poggendorff Illusion is an optical illusion that involves the brain's perception of the interaction between diagonal lines and horizontal and vertical edges.
		It is named after Johann Poggendorff, who first described it in 1860.
	www.encyclopedia-glossary.com /en/Poggendorf-Illusion.html (153 words)

	EGR 1170 C1 - Course Resources (Site not responding. Last check: 2007-10-09)
		This is the classic Muller-Lyer illusion that asks the question whether the two lines are of the same length or not.
		These optical illusions are drawn in a way in which tricks the eyes and makes things distorted.
		It shows a few visual illusions such as the rising star, ghost, the crazy type and a couple of question to see how easily you are fooled.
	www.prism.gatech.edu /~ce1770a1/EGR_PROT/trick.htm (2018 words)

	PsychSim -- Visual Illusions (Site not responding. Last check: 2007-10-09)
		Summary Students test their sensitivity to the Müller-Lyer, Ponzo, Horizontal-Vertical, and Poggendorf illusions by adjusting the length of a line in order to match the apparent length or position of another.
		For each illusion, students go through 4 trials without feedback, and then see a graph of their results.
		The graph is interpreted, and an explanation of the illusion is provided.
	bcs.worthpublishers.com /exploringinmodules5e/content/psychsim/6illusion/illusion0.htm (121 words)

	Poggendorf Illusion (Site not responding. Last check: 2007-10-09)
		The Poggendorf Illusion is a misalignment effect produced by the interaction of diagonal line elements with horizontal and vertical edges.
		Although the line segments in each picture are collinear, the right segment looks too high to be continuous.
		The right segment is seen as farther away and therefore higher in the visual plane.
	epsych.msstate.edu /descriptive/Vision/Poggendorf/pog02.html (119 words)

	Optical Illusions
		The direction of the angles at the ends of each line creates the illusion.
		In this optical illusion, when the red lines connect the fl ones, the color flows out of the intersecting lines and appears to create a circle.
		Look closely at this tube for a minute or so, and then decide if you are looking down the tube from the right or the left.
	www.visionrx.com /library/optical_illusion5.asp (167 words)

	Optical Illusions Etc: free, scary, word & picture illusions (Site not responding. Last check: 2007-10-09)
		These Optical Illusions are presented on this blog in the spirit of providing an entertaining venue to educate those interested in optical illusions and expanding the traditional assumptions of what constitutes an optical illusion.
		Some of the optical illusions on this blog may cause dizziness or possibly epileptic seizures.
		An optical illusion is any illusion that deceives the human visual system into perceiving
	illusionsetc.blogspot.com /2004/05/what-are-optical-illusions.html (840 words)

	MCDB 3650 - Visual Illusions
		Illusions examined first will be visual illusions on the Web.
		Keep this in mind and try to postulate mechanisms that give rise to the illusions you will study in the rest of this section.
		Illusionworks has lots of great illusions that I hope you will explore, but be sure to see:
	mcdb.colorado.edu /courses/3650/illusions.html (313 words)

	PERERA - PSYCHOLOGICAL SOFTWARE/LAB MODULES
		In this illusion, two equal length lines appear of unequal length when arrowheads are placed at their ends.
		In this illusion, a vertical line appears longer than a horizontal line even though the two lines are actually the same length.
		The Poggendorf program allows the researcher to present the Poggendorf Illusion using one of the three classical psychophysical methods.
	www.chss.montclair.edu /~pererat/persoft.htm (10925 words)

	Menstrual Synchrony...or Menstrual Illusion? (Site not responding. Last check: 2007-10-09)
		In an optical illusion, he explains, our brain fills the gaps, and although people take it for granted that seeing is believing, optical illusions prove that’s not true.
		“Illusions also prove that our brain is capable of imposing structure on the world,” he says.” “One of the things our brain is designed to do is infer the causal structure of the world from limited information.”
		So perhaps it makes more sense to reinterpret menstrual synchrony as menstrual illusion, best listed alongside other illusions, such as the Poggendorf illusion, Staircase illusion, Vase/Faces Illusion, and so on.
	www.menstrualmonday.org /coincidence.html (679 words)

	Peer Mentor's Visual Illusions (Site not responding. Last check: 2007-10-09)
		The same intensity light is reflected/transmitted all the way along the white spaces in the grid and yet the intersections appear gray.
		Some have theorized, that in the case of the spiral, the overlapping arcs and checkered background force your eyes inward to the center, thereby creating the illusion of the spiral which your brain finds irresistable.
		The images are exactly the same except for the thick fl area in the left image (an example of the Poggendorf illusion (1860)).
	psych.fullerton.edu /mentors/entert.htm (468 words)

	Perception (Site not responding. Last check: 2007-10-09)
		Click on the fl button labeled 'reveal illusion' to see how close the judgement is. NOTE: The graphic nature of the lines provide alternative cues about the angles of the lines potentially ruining the demonstration.
		Interestingly, the illusion is not well understood - though it could be based in perceptual ambiguities caused by the juxtaposition of curved and straight lines.
		This site shows 2 pictures: the illusion (2 apparently continuous diagonal lines passing through a vertical fl bar) and the same image without the bar (revealing 3 lines that are not in fact continuous).
	psych.la.psu.edu /clip/Perception.htm (9173 words)

	Sensation & Perception (Site not responding. Last check: 2007-10-09)
		It includes some types of illusions that are not discussed in your textbook.
		This site includes many optical illusions, including the work of M.C.Escher, the use of tessellations and their importance in perception and art and in learning mathematics.
		As we discussed in class, this perceptual illusion has caused more airplane crashes into moutains, head on collisions and near misses in the air.
	www.psyking.net /id44.htm (700 words)

	Poggendorf Illusion Start Page (Site not responding. Last check: 2007-10-09)
		The purpose of this experiment is to measure how the magnitude of the Poggendorff illusion is affected by changes in the separation of the vertical line components and changes in the length of the diagonal line components.
		Twenty-four randomly ordered trials are used to obtain 4 replicate measures under the 6 experimental conditions shown below.
		Begin the Poggendorff Illusion Experiment Download Authorware Source Files
	psychexps.olemiss.edu /Exps/Poggendorff/startp.htm (110 words)

	Poggendorf Illusion (Site not responding. Last check: 2007-10-09)
		This experiment will attempt to quantify the visual distortion caused by the Poggendorf illusion, using the method of constant stimuli, formalized by Gustav Fechner.
		The computer will present an image of a box with lines emerging from the lower left and upper right corners (see the figure below).
		You will judge whether or not the comparison line is too high or too low relative to a point (i.e., see "True Connection Point" in figure below) at which the standard and comparison lines would appear collinear.
	epsych.msstate.edu /descriptive/Vision/Poggendorf/pog07.html (123 words)

	Comments on 5908 \| MetaFilter
		More information on the aforementioned Poggendorf illusion, including a kewl little Java applet that demonstrates the effect.
		The use of perceptual illusions happens at a lot of these kinds of attractions (like the one in the Bay area), but the Oregon Vortex not only uses perceptural illusions but also has a very real phenomenon -- albeit completely within the laws of physics.
		Copperfield's Statue of Liberty illusion was done with a huge turntable, by the way.
	www.metafilter.com /mefi/5908 (4062 words)

	Visual Illusions
		Ambiguous Illusions: Your visual system interprets the scene in more than one way.
		Distortion Illusions: Illusions that distort an image's size, shape, and length.
		Plank Illusion-(this video takes a while to load).
	www.hornell.wnyric.org /interweb/visual.htm (168 words)

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