Talk:Optical illusion

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what is an optical illusion?

An optical illusion is any illusion that deceives the human visual system into perceiving something that is not present or incorrectly perceiving what is present - Adrian Pingstone 16:51, 31 Mar 2005 (UTC)
I've updated the definition to this: "An optical illusion is a type of illusion characterized by visually perceived images that are deceptive or misleading [1]. Information gathered by the eye is interpreted by the brain to give the perception that something is present when it is not." Although "visual system" includes the visual cortex in the Wiki defintion, it should be made clear that it is the brain that is deceived and not the eye. Also, optical illusions can deceive other species besides humans. Edwardian 07:09, 27 September 2005 (UTC)
is a concept created by the brain that guides you to see something that does not realy exists or is only an illusion created by the usual shapes, or movement of a picture

External links[edit]

Why did someone remove the links to two museum? -- User: 19:15, 22 August 2005

Well one good reason would be because the links were to web pages in German. For a subject like this a German language link isn't really appropriate on the English Wikipedia. The other reason would be that the anonymous editor adding the links (along with yourself) were adding much the same links to a large number of pages- this is often taken as spam linking. -- Solipsist 18:32, 22 August 2005 (UTC)..

Could please explain to me what is cognitive about stereograms? My understanding (which I belive is supported by the article about stereograms) is that stereograms use disparity information, which is has nothing to do with cognitive processing (at least in the way the term is used here). I believe that the statement "Stereograms are based on a cognitive visual illusion" is inaccurate. Any opinion? --Dontaskme 05:12, 23 August 2005 (UTC)

Would it be all right to add an external link to Visual Illusions and Impossible Objects which is a collection of Java driven simulations? Me thinking is that this is by far a more informative link than that to Wolfram's Project. 12:40, 15 September 2008

Broken link?

Is this link loading for you? It is not loading for me. (I did not remove it from the external links.) 10:30, 30 July 2006 (UTC)

Yes, it is loading.--Mahadevan Subramanian (talk) 14:43, 8 July 2008 (UTC)

What is the Name of This Illusion?[edit]

First time I've seen it. One of the most intense illusions I've ever seen, I wish it could be linked to the page, but I don't know the name of it, or what class it belongs too. Anyone know anything about it?--Brentt 00:20, 14 October 2005 (UTC)

First time I've seen it. Way cool. Don't know a name for it. Very impressive. I think it's a very artistic exploitation of two well-known illusions. First, the pink dots disappear because they're "stablized." If I stare at a real scene in fairly subdued light (e.g. interior of an auditorium) and really fixate hard for a couple of minutes, the entire scene will almost grey out for brief periods of time but even a tiny eye movement will cause the scene to reappear with a strange sort of bas-relief effect in which only the edges of objects become visible. Here, by using dots that have blurred edges--and, I suspect, a luminance that matches the background--the effect of small eye movements is reduced. Second, the appearance of the green dot is just simultaneous contrast.
Unlike some of the truly weird illusions that obviously depend on high-order processing, I think this one could be explained simply on the assumption that parts of the retina (or spatially mapped parts of the brain behind it) that correspond to the pink dots gradually adapt and become less sensitive to red. Dpbsmith (talk) 13:34, 13 October 2005 (UTC)
This is the second time I've seen it this week, so it must be a new one making the rounds. It appears to be a combination of two physiological illusions. I agree with Dpbsmith's explanation for the disappearance of the pink dots; I believe this is an example of the Troxler effect. I believe the appearance of the green dot is simply an afterimage due to fatiguing of the red-sensitive photoreceptors. Edwardian 16:42, 13 October 2005 (UTC)
A Google search on "rotating pink dot" turns up 17 hits but no clear indication of where it originated or who devised it. People are just copying the animated gif, it seems... Dpbsmith (talk) 01:05, 14 October 2005 (UTC)
That's unfortunate. I'm going to make sure when I copy things like that to try and include the discover's name, or atleast the common name of the illusion, so people like us can find info on it and the person who made it can get due credit for now on. --Brentt 02:35, 14 October 2005 (UTC)

Got it! A google search for "rotating green dot" turned up, for the first hit, this page that calls the illusion "Lilac Chaser", its a website with several other animated optical illusions called Michael’s “Optical Illusions & Visual Phenomena”. Most of the illusions tell a little about the source. Some are old illusions originally made by ingenius mechanical appartuses (apparati?), some pictured like this one. For the lilac chaser the site also gives you 3 interesting controls to vary the speed, color saturation, and a few different color schemes. Varying the parameters while focusing on the center makes for some very interesting effects. Also I found that if you gaze off center you get some interesting effects. I wish they would make a parameter to control the position of the "+" and let it move, I found even if you gaze near one of the pink dots the effect still works.

Thanks for the idea for the google search Dpbsmith, I didn't spend much time trying to think of a good search phrase, but your search phrase made it a matter of a simple step from pink->green.--Brentt 02:46, 14 October 2005 (UTC)

what about this one, similar but not the same. What are these called?

Physiological vs. cognitive illusions[edit]

The article lists many sub-categories of illusions that should fall under the broader categories of either physiological illusions or cognitive illusions. I've made a change to reflect that. Edwardian 06:18, 3 November 2005 (UTC)

Necker cube[edit]

The article says:

The Necker cube is a well known example, the motion parallax due to movement is being misinterpreted, even in the face of other sensory data.

I'm kind of confused by what it means by "motion parallax" and what the "other" (in addition to what?) sensory data is supposed to be. NickelShoe 15:26, 17 November 2005 (UTC)

Choice of examples[edit]

The top illusion is incredible. But I don't seen any black dots on the next one. Unless I'm a rare exception, it should be replaced, e.g., with something like the top hat or other line ois.

I thought the dot one was awesome. I can't believe you don't see it. Don't stare at it; move your eyes around it. NickelShoe 04:52, 17 December 2005 (UTC)
::I tried that.  I don't see any dots (I wear glasses; maybe that makes a difference).

Impossible Figures are Optical Illusions?[edit]

It seems to me that impossible figures, like Penrose's drawings, are distinct from optical illusions. How are they optical illusions? It seems to me that they are no more optical illusions than a perspective in drawing. So how are they optical illusions again?--Brentt 07:43, 17 December 2005 (UTC)

But isn't perspective in a drawing a kind of optical illusion? It's just a matter of interpreting things in a way that isn't held up by what's actually there. Perspective in a drawing uses foreshortening and whatnot to give a 2D image the illusion of three dimensionality. I mean, if perspective and impossible objects don't count, then neither should the Necker cube, for instance. We try to interpret impossible figures as real figures, even though they're self-contradictory. It's just a particular kind of illusion, right? NickelShoe 13:48, 17 December 2005 (UTC)


or something has some optical illusions Randomkeys 03:56, 3 August 2006 (UTC)

Example Duplicates[edit]

A lot of the illusion examples are duplicated under different names. Someone should go through and remove some of them.

Research in use of illusions[edit]

While illusions are cool and all, very few people ever postulate utilitarian uses for them. I myself have done research in this field, so I can't add anything, but perhaps someone would like to look over my stuff (especially my bibliography) and see if there is anything worthy of inclusion? Optical Illusions in Computer Graphics capnmidnight 04:09, 11 October 2006 (UTC)

Floating Faucet[edit]

I noticed that there is no mention of where this sculpture is located. Can the person who added the pic please at least tell us the city and country, if not the name? Thanks. Raphael 21:23, 23 October 2006 (UTC)

optical illusion is really weird and they are soo cool and they should have more and they need more color

There are a few floating faucets around the place, they have one at my local swimming pool ;)

spheres image[edit]

Is it just me or the "larger" sphere is actually larger? 06:50, 14 March 2007 (UTC)

Roflcopter.FiringRange 17:17, 12 October 2007 (UTC)

Split into List of optical illusions[edit]

There are currently 71 articles listed in Category:Optical illusions, most of which are short stubs, no more than a few sentences long. Some of the articles are duplicated where an illusion may have two different names (ex: Impossible cube and Necker cube). I think we should take those articles along with the list from Optical illusion#Well-known illusion and merge them into one large article, List of optical illusions. There all the illusions can be listed, and for the few that are not stub articles, their article will remain as is, but can still be added to the list article with a {{main}} template to link them to their respective main article. I think it's a good idea, but I don't want to start creating it until I get some feedback. Plus I wouldn't mind having any volunteers to help me out. –Crashintome4196 02:59, 20 April 2007 (UTC)

I wouldn't say merge the stubs, but I think having a separate article for the list is a good idea. Jon Fawkes 04:09, 24 April 2007 (UTC)

Same Color Illusion seems flawed[edit]

Are the squares A and B of exactly the same shade? hide the rest of the picture and simply compare the two squares. I but they'll look very different shades.

Good thing you weren't betting cash, or you'd be that much poorer. The two squares are exactly the same shade. You may be able to tell with some extreme squinting, or just have a tinker in photoshop if you can't. GeeJo (t)(c) • 14:56, 11 June 2007 (UTC)

Colors ARE different. Copy/paste them into photoshop and you will see that they are different. Whoever made that picture simply altered the whole picture (including the test squares). —Preceding unsigned comment added by (talk) 08:36, 12 May 2008 (UTC)

No they are the same. Copy it to some graphics program, rub out everything except bits of the 2 squares. They look exactly the same.--Hamster X (talk) 12:59, 14 May 2008 (UTC)
I agree that A and B are exactly the same shade, but to me they seem obviously the same (ie, it's a bad illusion). The grey bar illusion later in the article illustrates the same color illusion much more effectively. Perhaps my vision is too poor and the A and B are too small for me. Or perhaps my laptop LCD doesn't show contrasts optimally. Is this illusion more obvious in print form?Pdcook (talk) 01:55, 23 September 2009 (UTC)

Proposed merger[edit]

This page is extremely similar to the "Illusion" page. Therefore, it should be merged under the name "Illusion." Dewarw 16:35, 15 June 2007 (UTC)

See further discussion on Talk:Illusion. Andreas Kaufmann 21:19, 26 June 2007 (UTC)

Pink card / colour cast illusion[edit]

The pink cards look different because they are different. The RGB values for the lighter pink card are sufficiently close to each other to be allowed to be called the same. However, the right-hand card is distinctly different in each case. I get RGB: 172/159/239 vs 185/134/226 when measuring them in Photoshop. This image should be replaced with a better example - or simply removed. Sorry... I don't have a Wikipedia account and (a) currently have no interest in getting one and (b) don't have a better example to offer, so I won't presume to make any edits to the live article. 18:52, 28 August 2007 (UTC) Gary Smith

Er, it's only the second card from the left that's meant to be different. I will correct the caption to make it more obvious. Mike Young 20:05, 29 August 2007 (UTC)

I don't get it. I see all of the cards as being a slightly different shade of colour, not just the pink one. And the difference is not very distinct.--Hamster X (talk) 13:02, 14 May 2008 (UTC)
I dont see it either, the pink cards look the same to me in both pictures. the other cards ARE different (can just use MS Paint to figure that out)-- (talk) 03:18, 20 October 2008 (UTC)

Vision Distorter illusion[edit]

The original design for the animated diamond illusion near the top (currently unreferenced) of the page was in fact originally from The illusion, called "Vision Distorter" can be dated back to June 2002, as recorded by*/

(scroll down to Vision Distorter)

Here is the image location (unresized): [1]

If it's okay, I may add a URL link to the appropriate page.

In all fairness, and according to Michael Bach's site, the very original rotating spiral was created by Joseph Plateau in 1849, and a 3 tier version by Jerry Andrus later. The two tier version at Skytopia was inspired by the very original by Joseph, but independently of Jerry's 3 tiered version (the diamond effect on the Skytopia version is a novelty in any case). --Skytopia 03:31, 15 October 2007 (UTC)

Barrel vs Pincushion - 3D depth?[edit]

I noticed this while reading the Image distortion article. The curved lines appear to give a 3D experience of near/far. Basically it is like looking at a wire-mesh sphere, looking at the surface from the outside vs being in the center of the sphere looking outward.

Center appears to be close to viewer.
Center appears to be far away.

I don't see this one described in the links list. A "new" illusion? We'll call it the "Mahalko Illusion". Um, yeah. ;-) DMahalko (talk) 06:12, 9 July 2008 (UTC)

Related to this, Would the image File:Pressure Vessel.jpg be helpful. Exit2DOS CtrlAltDel 14:39, 1 February 2010 (UTC)

Deleted Image[edit]

I'll delete this image "My Wife and Mother-in-law" because no one will get it (not even me) and it just hurts my brain. It is not written how it will work. So yeah, good image.

My Wife and My Mother-In-Law (Hill).svg —Preceding unsigned comment added by (talk) 18:40, 30 December 2008 (UTC)

The chin of the 'wife' becomes the nose of the 'mother-in-law,' and the black line that looks like a necklace on the'wife' becomes the mouth of the 'mother-in-law.' Hope that helps. —Preceding unsigned comment added by Krazieeee (talkcontribs) 17:57, 14 January 2009 (UTC)

It is said that female viewers will first see mother in law and male viewers will first see wife. —Preceding unsigned comment added by (talk) 17:46, 21 April 2009 (UTC)

What Is The Name Of This Illusion?[edit]

[2] It's one of the best I have seen. Has it got a proper name? —Preceding unsigned comment added by (talk) 15:44, 12 August 2008 (UTC)

List of optical illusions[edit]

The section with the list of optical illusions is now redundant as the article List of optical illusions now exists. I am a bit stuck and cannot figure out the new section titles. I have done my best. Please tweak it to your liking. Thanks. Anna Frodesiak (talk) 00:47, 27 May 2010 (UTC)

Quantity of images[edit]

15 images may be a smidgen too many. Anna Frodesiak (talk) 00:55, 27 May 2010 (UTC)

"Four eyes" illusion[edit]

Maybe not exactly an illusion but it is very weird to look at. Scientific American briefly mentioned it. GregorB (talk) 21:17, 25 January 2011 (UTC)

square b is mislabelled[edit]

square b is mislabelled

b is clearly a light square while a is a dark square logically they can never be the same shade else there would be no little squares just one huge one

for be to be the same shade as a it has to be a dark square hence the label << b >> needs to be moved one square downward

that would result in a and b both labelling dark squares while the appearance of a and b would be different shades even though they are identical — Preceding unsigned comment added by (talk) 18:26, 14 February 2012 (UTC)


Is it just me or is there an optical illusion (same type) for these two logos? File:Game Developers Conference Logo.png File:Apteralogo.png

What's the name of this type of illusion? I think this illusion occurs because our eyes are accustomed to closing a circle, but these aren't complete circles, so it looks like the straight lines are curving towards the point, making the right angle look like a slight acute angle. This should be added into the article as well. - M0rphzone (talk) 04:26, 8 April 2012 (UTC)

I'm not seeing what you're seeing. Are you referring to the teardrop shape in each logo? The vertex looks like a right angle to me, but maybe that's because the angle lines make no pixel jaggies on my monitor. ~Amatulić (talk) 16:43, 29 May 2012 (UTC)
Yea, the apparent teardrop shape illusion. If you cover the rest of the circle, the vertex looks like a normal right angle, but once you look at the whole thing, it looks teardrop-shaped as if the lines curve inwards before meeting at the vertex. - M0rphzone (talk) 05:16, 24 August 2012 (UTC)
I think I've found the answer. This may be a form of the Law of Closure. We percept the curving of the corner because the brain tries to "close" the circle. - M0rphzone (talk) 02:57, 1 October 2012 (UTC)

Edit request on 18 November 2012[edit]

Missing reference for Cognitive Illusions:

Gregory, R. L. (1997). Visual illusions classified. Trends in Cognitive Sciences, 1(5), 190–194. doi:10.1016/S1364-6613(97)01060-7 (talk) 06:25, 18 November 2012 (UTC)

Hi! What part of the text is sourced with your reference? Lova Falk talk 14:31, 18 November 2012 (UTC)

Image queue[edit]

As suggested in Wikipedia:Image_use_policy#Image_queuing, I create a public image queue below and put an (animated) image there that is quite similar to "Cubes in same/increasing height" which are currently shown in the article's gallery. Jochen Burghardt (talk) 19:48, 16 July 2013 (UTC)

How do I link to a page on a book?[edit]

Page 33 of the book 'Incognito' spells out that Hermann von Helmholtz pioneered this stuff in the mid-1800s. I tried to link to a page through Google Books, but it didn't work exactly. Can anyone correct it, please? SMSophiahounslow (talk) 14:44, 14 August 2013 (UTC)

You go to the page you want and then click on the icon that looks like a chain to get the link to that page. I attempted to fix it for you, although often specific page references won't work because Google Books hides random pages or large sections of the more recently published books. ~Amatulić (talk) 17:23, 14 August 2013 (UTC)

Proposal to rename the page to "Visual Illusions"[edit]

The old term "optical illusions" is considered outdated in the scientific community (IMO) since it seems to imply that the eye or the optics of the eye are somehow involved (which is rarely if ever the case). I believe the page should be renamed to "Visual illusions", and there should be a redirect from "Optical illusions" to that. Strasburger (talk) 12:33, 13 August 2016 (UTC)

No, that isn't going to fly: “Optical illusion” is by far the most common name for these phenomena; compare 24 million results (gsearch for “optical illusion”, to 425,000 hits (gsearch) for “visual illusion”. Do you have any evidence that the term is considered “old...[and]... outdated in the scientific community”?
And you may have a point that it's a misnomer when the optics of the eye aren't involved, but the article here currently suggests the opposite; that the term “visual illusion” applies mainly to pathological conditions of the eye (ie optical effects) rather than to the cognitive stuff (ie visual effects).
You may have an uphill battle on your hands with this one! Moonraker12 (talk) 13:14, 24 August 2016 (UTC)
I agree that the term “optical illusion” is the traditional and far more common one. Still it is considered outdated by most if not all of the scientific community studying visual perception and illusions of seeing. The world’s main scientific conferences on the matter are the European Conference on Visual Perception (ECVP, (which I have attended for over thirty years now), and the Vision Science Society (VSS, (which I used to go to regularly). Both conferences have a contest for illusions every year (, The illusions shown on the Wikipedia page belong to that category (e.g. the Adelson “checker shadow” Illusion shown prominently as first example). There is further a scientific journal that has regular papers on illusions (iPerception,
I do not know a single "optical illusion" where the optics of the eye play a major role, or even a role at all. The term "optical illusion" in fact derives not from optics, but from the Greek word for "seeing", and in the original sense of referring to an "illusion of seeing" the term is correct.
And, yes, you are right when saying that the article currently suggests that the eye is involved and that the term “visual illusion” applies mainly to pathological conditions. So that needs to be corrected (I could do that after the ECVP), or else all of the examples need to be removed (which of course does not make sense). Strasburger (talk) 14:54, 24 August 2016 (UTC)
At the University here in Italy, from Kanizsa onwards we have studied the perceptual illusions often even after Gibson. In any case, the reasoning of Strasburger is scientifically perfect. -- (talk) 15:41, 30 August 2016 (UTC)
  • It doesn't matter which term is more accurate or current, as far as Wikipedia is concerned. "Optical illusion" is the common name and so we go with that. "Visual illusion" is too vague for our purposes; if you google it, you actually get more hits for "optical illusion". freshacconci talk to me 15:53, 30 August 2016 (UTC)