Talk:Depth perception

Discussion1

1. Oculomotor – sense the position of our eyes and the tension of the eye muscles (only close range) - Convergence Inward movement by near object - Accommodation Changing of the shape of the lense 2. Monocular – cues that work with one eye

     - Prictorial Cues
        Source of deep information...?

- occlusion (one object hides a part of the other) [whole range] - relative hight (higher is futher away -> horizont) [works by close & medium range] - cast shadows (shadow to help to locate the depth) - relative size (by known same size objects -> smaller one is futher away) [whole range] - familiar size (by know differen size objects, same size -> the known smaller one is closer by) - atmospheric perspective (distance objects are less sharp (on the earth -> air)) [long range] - linear perspective - drawing system of linear perspective (duplicates the pricorial depth cues) ??? - depth cue of linear perspetive (due converge of very far lines (imagine: railway tack)) - texture gradients (depth information from the ground)

      - Movement-Produced Cues

- Motion parallax [works by close & medium range] - > far objects move slowly; near objects move rapidly -> same when you look on the Retina (far objects move less) - Deletion & Accretion - > deletion (covered up) & accreted (uncovered) when moving more closely -> related to motion parallax & overlapping 3. Binocular – cues that depend on two eyes [works by close & medium range] Binoocular Disparity and Steropsis!!!

|-> different image of the two eyes  	|-> Impression of depth created by disparity

just a question about perseption.. if anybody knows a formula for how to measure diminishing sizes over distance. for example: how large would a 20m tall object appear if it is 8 kms away? —Preceding unsigned comment added by Inforlife (talk • contribs) 09:51, 27 February 2010 (UTC)

Discusion2

The page doesn't provide any information about why depth perception fails, or why people with failed depth perception experience doubled vision when viewing 3d animated images designed to be viewed with shaded glasses with such glasses Hackwrench 04:56, 27 September 2005 (UTC)

As you wish. I've added a blurb on amblyopia and strabismus for starters. Edwardian 07:22, 27 September 2005 (UTC)

Discussion3

I feel that the part that says "our depth perception was, in a way, created by trees", while being an amusing image, doesn't belong in a resource like wikipedia. Anyone agree/have evidence from the style guide?? 213.48.15.234 14:53, 20 February 2007 (UTC) u have no idea what u sayin — Preceding unsigned comment added by 72.0.44.191 (talk) 21:34, 28 February 2012 (UTC)

Monocular cues

Monocular cues are a particularly important subject for video games designers and quite complex ones are dirctly supported by high end video cards.

I believe Motion parallax is more important to humans than indicated. Nodding an object up and down on a screen with a frequency as would be seen when walking seems to give a much better impression of 3D than does waggling it side to side - intuitively one might have expected the side by side comparison to be better because of binoular vision - it'd be interesting to see if people who never could walk have the same experience. Dmcq 07:57, 24 June 2007 (UTC)

Philosophical implications

What the fuck is this shit? 121.45.15.32 15:28, 17 August 2007 (UTC)

That's right. I removed the section. See below:

Depth perception is (along with sexual reproduction), a convincing real-life example of the "thesis+antithesis>synthesis" model of progress developed by Hegel, Fichte, and Engels. Dialectics, including dialectical materialism, derives from the idea of a dialogue between people representing different points of view on a subject, who arrive through argument at a new way of seeing the subject that preserves whatever remains valid from both sides of the discussion (as in the Socratic dialogues of Plato). Binocular vision is a sort of argument between one eye (thesis) and the other (antithesis), each seeing the organism's environment from a slightly different perspective, which the brain resolves into a three-dimensional image containing contributions from both but transcending their limits. As in any good synthesis, depth perception is an almost magical leap to a higher level, embodying a "qualitative change" that could hardly have been imagined or predicted, by examining its component parts.

Response to the above deletion & obscenity

Why this section must be purged:

Cardinal sin 1: suggests there might be philosophical implications to be found in sensory experience. How to avoid this kind of error: Sensory experience must be discussed only in terms of electrochemistry etc., the drier the better. To imply that some sort of "consciousness" or "self" or "spirit" is what does the experiencing is anti-scientific, in so far as [i] the existence of consciousness is not only unproven; it is disproven see, (e.g., Skinner, B.F., Beyond Freedom and Dignity). [ii] any emphasis on "the subject" (that which experiences) opens the door to subjectivity, to Romanticism, and hence to the kind of occult rubbish that has no place in an article on a scientific subject.

nota bene:What distinguishes Wikipedia from archaic "encyclopaedias" is that our most fundamental principle, n.p.o.v., is consistent with the fact that consciousness does not exist. This represents a quantum leap over all previous efforts, e.g., Diderot, Britannica, et al. Egregious examples of the corrosive effect of p.o.v. abound in the Britannica in particular, whose authors are often publicly idenified with the subjects they write on, and tend to use 'colorful' or 'poetic' language to sell their idea (and what is an idea, after all, but a p.o.v. that takes on a life of its own?) See for instance, in the 14th edition, Einstein's "Space-Time" or Liddle-Hart's "Strategy".

nota more bene: Maintaining n.p.o.v. in approaching this particular topic, depth perception, is even more necessary than usual, since depth percption itself might, at first glance, seem to validate the importance and usefulness of the p.o.v. Indeed the danger is doubled here, if you agree with the deleted text's dubious assertion (backed up by no citations) that two p.o.v.'s are required for binocular vision. (Or trebled, if you accept its mad, mystical notion that the brain's visual cortex somehow synthesizes these two p.o.v.'s into yet a third p.o.v. even more seductively "magical" than its component p.o.v.s.)

Cardinal sin 2: offers biological, experiential examples (i.e. binocular vision, sexual reproduction) to embody and validate philosophical concepts. Please follow these guidelines:

a. Philosophy must be discussed only in terms of philosophy itself, through: (1) discussions about discussions about discussions, and (2) footnotes/links refering to discussions.

b. Discussions of philosophy must include (1) no nouns that refer to anything tangible, (2) no verbs that suggest physical action, (3) no adjectives that evoke any [i] color or [ii] smell.

c. The passive voice is to be used whenever possible.

d. If a definition of a word or term is required, the defintion itself must always be more (not less) abstract and scholarly than the term defined. To "anchor ideas in real life" is vulgar anti-intellectual populism, and hence anathema to legitimate (i.e., abstract) philosophizing.

All kidding aside now. If you weren't wasting your life trolling around purging the meaning out of all the information you can catch, you'd have more time to learn something about philosophy, about real life, and about how to see what's right under your nose with your own eyes. And if you (or anyone else) ever really want to know "what the fuck this shit is" get in touch. There's an easy ten-second visual exercise anyone can do that makes it all crystal clear. Chelydra (talk) 06:11, 30 September 2008 (UTC)

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Squirrels

"and squirrels, which move in lines orthogonal to an object of interest to do the same"

Is there a more specific source for this? The supplied link is to the front page of purveslab.net, and I can't find anything there.

Koala man 00:14, 23 August 2007 (UTC)

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binocular vision not necessary

"In modern terminology, stereopsis is depth perception from binocular vision through exploitation of parallax. Depth perception does indeed rely primarily on binocular vision, but it also uses many other monocular cues to form the final integrated perception. There are monocular cues that would be significant to a "one-eyed" person, and more complex inferred cues, that require both eyes to be perceiving stereo while the monocular cues are noted. This "third" group relies on processing within the brain of the person, as they see a full field of view with both eyes."

This article is not as bad as I expected -- but the lead is muddled. The plain fact of the matter is that depth perception does not require binocular vision. People who have binocular vision think it is much more essential than it seems to be to people who have never had it.-69.87.203.221 22:54, 11 September 2007 (UTC)

At sometime in the distant past, I saw a graph that came out of a US airforce study into depth perception mechanisms. They listed:

• Focus: The amount of muscle tension required to distort the lens of the eye to make a sharp image.
• Stereopsis: The amount by which the eyes have to point inwards in order to 'fuse' a single image.
• Parallax: Small head motions causing objects in the foreground to move by a bigger amount than those in the background.
• Object size: You know how big a car is in reality - so comparing that to the size on your retina tells you its distance.
• Atmospheric dispersion: At long distances, the attenuation of green light and the general mistiness of the scene can give you range cues.
• Earth curvature: At extremely long distances, the curvature of the earth itself becomes a distance cue.

Each mechanism was shown as being effective over some span of distances with a roughly gaussian shaped curve for each - but the brain is good at getting an accurate range estimate even when one or more of the mechanisms is giving false or inaccurate information. Very close up, you can't cross your eyes enough to fuse the image - so focus dominates range estimation out to a few feet. Out to (IIRC) 20' or so, stereopsis dominates - but beyond that, you can't measure the angles accurately enough and parallax takes over - and throughout the whole range of distances, object size and atmospheric dispersion have an effect. Only at very long ranges does earth curvature have an impact. If one or more of these mechanisms is impaired (eg if you are blind in one eye) then the other effects can compensate to some degree. Several observations back up these assertions:

• When people first start wearing glasses or contact lenses, they can find range estimation over very short distances difficult.
• Astronauts on the moon - robbed of object size by the fractal nature of cratering and having no atmospheric dispersion cues to fall back on found it hard to estimate distances beyond ~100 feet.
• A very common defect in vision at birth in about 10% of people results in a crossing of the eyes. If this is not attended to within a fairly short amount of time (weeks or months - but not years) then these people (with two perfectly good eyes) frequently fail to develop a stereopsis sense because even though the eye-crossing sorts itself out within a year, the part of the brain that deals with stereopsis never develops. In recent years, this is tested for - but generally, 5% of people do not use the stereopsis mechanism at all.

SteveBaker 15:47, 12 September 2007 (UTC)

Actually, stereopsis is not "The amount by which the eyes have to point inwards in order to 'fuse' a single image". I think you confused it for vergence. Stereopsis is normally referred to as the process of fusing the two different retinal images as a result of binocular disparity. --Arthur Lugtigheid 13:19, 27 October 2007 (UTC)

Binocular vision IS the fundamental component of depth perception...

...although there are many other ways of perceiving depth— that is, there are other factors that can to some extent simulate or supplement binocular vision. These other factors should certainly be included and explained in the article, but the distinction should be kept clear. This is a matter of scientific claritication, not philosophical quibbling. An analogy would be sex. In our subjective experience, there are all kinds of "sexual experience" which many of us find more erotic and satisfying than heterosexual intercourse, and all of these deserve to be included in an article titled Sex. However, the fundamental scientific fact about sex is that it's how most species (the interesting species anyway) reproduce themselves, with male and female organisms mingling their genetic information at a cellular level. The pleasurable sensations that accompany this act can be more or less duplicated by all sorts of other means (far too many to list here). People who are unable or unwilling to engage in heterosexual intercourse, or engage in it but prefer other varieties of "sexual experience", will tend to regard it just one option among many that are commonly included under the rubric of Sex — and subjectively, that's entirely valid. (In the other direction, we now have IVF and other technologies that can accomplish the reproductive funtion of sex without its pleasure or emotion. We can have sex without reproduction, and reproduction with sex.) Objectively, however, the old-fashioned way of sharing love, pleasure, and DNA, all at the same time, is what sex is all about. Objectively, everything else is a simulation of, or a supplement to sexual reproduction. The analogy isn't quite exact, since making babies is absolutely necessary for survival as a species, while judging distances is merely very helpful. Therefore, if the other ways of judging distances (perceiving depth) worked just as well as binocular vision, this would all be pointless. But binocular vision is far more powerful and significant than any other way of judging distance distance visually, and it has affected hman anatomy almost as much as sexuality has (e.g., the shape of our faces, the form of our brains).. Nothing else comes close. Chelydra (talk) 09:06, 30 September 2008 (UTC)

I am not sure what your point is, what is so important about binocular vision as compared to the other forms of depth perception? What would you have different? Have you got references to other places showing the kind of thing you mean? Dmcq (talk)

The point? There are several points... It's not that the main page (article) is flawed or inadequate in its present form (although, as indicated above, I'd like to see "philosophical implications" back where it belongs, probably after a rewrite) — I'm just taking issue with the assertion that binocular vision is not necessary. Necessary for what? For judging distances in a very precise and reliable way, it's necessary — the other things that are helpful in perceiving depth/distance are less so, because they generally don't work as well. Those are mostly all visual cues or clues we pick up from the "information" in our environment — e.g. there will be more atmosphere between us and a hilltop ten miles away, than a house 100 yards away, so the hilltop will appear a bit hazy and washed out compared to the sharper, more vivid appearance of the house. Also, we'll see the hilltop behind the house, although we need binocular vision to tell us how far (a camera, or one eye, could easily be fooled by a well-painted flat backdrop hanging 10 feet behind the house, showing hazy hilltops). Binocular vision, however, isn't just another environmental phenomenon we perceive in the world around us and outside us — it happens INSIDE us, and it's a result of evolutionary progress that REORGANIZED us inside and out (from the neck up) for the purpose of depth perception. The need for reliable depth perception when "we" lived in trees moved our eyes to the front of our faces, and REBUILT OUR BRAINS in ways that lead directly to (or rather, prepared the way for) the front-brain explosion which defines us as a species.

One more point: If you look at any photograph, you'll see a picture in flawless perspective. It will contain all sorts of cues/clues about spacial relationships (depth, distance, form, etc). BUT if you look at a STEREO photo (in a Viewmaster or an antique stereoscope) the spacial relationships will open up, quite astoundingly. You can experience the same thing by simply looking around a room with one eye, then with both eyes. You're now seeing spacial relationships that really do exist in your environment (or in the scene photographed) but they were completely invisible to the camera lens or to a single eye acting alone. You're processing the information in a totally new way, and your ancestors spent tens of millions of years giving you this ability — in other words, the tree shrews and early primates kept falling down and busting their little heads whenever they misjudged the distances between branches, so those with front-facing eyes (and bigger brains to process the resulting information) were the ones that could survive and reproduce, and eventually emerge as YOU — with the kind of face you see in the mirror, and the kind of brain that can read this now. Hence, binocular is not only necessary for perceiving depth ACCURATELY, but also necessary for you to exist in your present form. Chelydra (talk) 07:10, 1 October 2008 (UTC) ADDENDUM: "Have you got references to other places showing the kind of thing you mean?" Well, if I can show you exactly "the kind of thing I mean" by showing you how to see it right under your nose, doesn't that serve the purpose, and accomplish in three or four seconds as much as 17,432 footnotes with scholarly citations? —Preceding unsigned comment added by Chelydra (talk • contribs) 07:17, 1 October 2008 (UTC)

What you are saying may seem obvious to you but it isn't what I would have thought of as straightforward common knowledge, I don't feel binocular vision is so uplifting or whatever. Depth perception is something people have researched and produced papers about. Therefore you would really need to cite some references to back up what you say. Otherwise it would at best count as orignal research and anything like it removed from Wikipedia for that reason. In fact I notice a very unencyclopaediac bit in the main article for instance which should really be changed or removed saying 'Try looking around at the room you're in with just one eye open...', the reader may only have one eye or be blind or not have binocular vision even if they have two eyes. Dmcq (talk) 08:37, 1 October 2008 (UTC)

What YOU are saying is that what you see if you (literally) open both eyes and see what's under your nose can't possibly be accepted as valid unless it's backed up by footnotes and links. Is Wikipedia supposed to be creating an alternate universe, or helping us understand the one we were born into? Chelydra (talk) 11:43, 1 October 2008 (UTC)

You're right about one thing — this is NOT at present "common knowledge", although it's certainly straightforward enough by any standards. As we spend more and more of our lives gazing into flat screens, we have less and less use for binocular vision, and as I think is generally known, the parts of your brain you don't exercise tend to not develop much. I can't offer citations offhand, but I'm quite sure I've seen references to reliable studies showing that kids brought up with TVs and computers have their intellectual development impaired in subtle ways as a result of rarely using "spacial reasoning". Among hunting-and-gathering groups, binocular vision is crucial — survival depends on efficiently grabbing berries and fruits (off a tree, or out of a brier patch), quickly judging distances in aiming and timing an arrow shot, etc. Personally I came to appreciate it through art studies — my teachers kept talking about "seeing the space" where there wasn't anything to see, and "drawing the back of the head" when you're doing a realistic front-view portrait. It was only when I had my own art students that I finally figured out those mystic-sounding teachers been teaching binocular vision. Or, to be more precise, they'd been urging us to use and energize the parts of our brains that process binocular vision, so our pictures wouldn't come out looking flat.Chelydra (talk) 12:01, 1 October 2008 (UTC)

One final thought - if you're one of the many folks who can't do so, please accept my apologies for telling you over and over to see with both eyes. —Preceding unsigned comment added by Chelydra (talk • contribs) 12:42, 1 October 2008 (UTC)

Please read No original research and more generally What Wikipedia is not. I'm pretty certain putting in anything like what's above would be quickly rejected and reverted on grounds outlined in those articles. You might wish it to be something else, if so you can discuss your views about what's wrong at the Policy section of the Village pump. How about considering the reader who wants to find out about depth perception. I think telling them to open their eyes and look and it's simply marvelous just doesn't cut it as part of an answer. Dmcq (talk) 17:49, 1 October 2008 (UTC)

Do you really not find anything odd about your insisting that using one's eyes must not be any part of the process of understanding vision? You really believe that actually seeing what binocular vision is by using it shouldn't even supplement the business of digging through links and footnotes to find words about it? Good lord! Chelydra (talk) 18:53, 1 October 2008 (UTC)

Can I just add to this that the extraction of binocular disparity information is only a viable cue to depth within a couple of meters from the observer? And if it comes to motion in depth, people are largely biased. In an evolutionary sense, I think scientists in biological research mostly agree that binocular vision has mainly evolved to assist for fine manipulations with our hands (think of threading a needle). This is, however, all speculation and supporting it with references is hard. Also, stereo-photography is not the best example here because the depth (or disparity) is usually not geometrically correct and is usually exaggerated to enhance your feeling of depth. --Arthur Lugtigheid 16:22, 20 April 2009 (UTC)

Generally, I'd say Chelydra's rant is useless without references, since it's not an incontrovertible fact and should be backed up by a reliable source. (see WP:RS, Chelydra). Binocular vision is the only mechanism that allows you to actually measure distance to objects mentally, true, but I'm not sure that makes it the "primary" determinant of depth. Use of parallax is an excellent cue, and suffices for many people lacking binocular vision. And as Arthur says, at a distance motion parallax and perspective are far more important determinants of depth than binocular vision. Graft | talk 18:59, 20 April 2009 (UTC)

Proprioception plus Depth Perception?

The brain takes proprioception, depth perception, and other resources and uses them all together to create a 3-D understanding of the world surroundings and the physical self located in and moving in the world. What is the proper term for the whole functioning brain 3-D model/ability?-69.87.200.68 11:27, 12 September 2007 (UTC)

Brain vs. eyes

"In physiology, depth perception is the ability of an animal's brain to interpret visual information in three dimensions."

In some ways, the disambiguation article has the better short definition. Depth perception usually uses input from the eyes, but it is really a brain thing, using whatever information is available. (That's why movies and TV work so well.) -69.87.200.68 11:27, 12 September 2007 (UTC)

Untitled discussion

So what is the difference between one's performance on depth preception and stereopsis? What dictates them? If one has different of 2 lines decimal visual acuity or more between eyes when uncorrected(and never had correction), would you expect a better depth perception or stereopsis after full correction to balance visual acuity? —Preceding unsigned comment added by 218.247.199.97 (talk) 12:57, 18 April 2008 (UTC)

Is this not just an aspect of visual perception? We need to decide whether that article contains all these elements, or if they are off in their own little articles, all cross-linked to each other and to other articles on related issues in the senses. For instance depth perception is related to motion and the kinesthetic sense since the relation of a moving body/observer to the observed environment is important to cognition and even in perception directly. All those attempts to get robots to come to conclusions about their environment with one eye and no neck, never worked. Two eyes didn't work. Only when the robots got two eyes and a neck, could they calculate their terrain with anything other than bizarre mistakes.

I think it deserves its own page, it is very important.

When somebody wants to integrate it. Just the basic facts, source Goldstein [(Goldstein, Sensation and Perception (Sixth Edition)].

The name of this article

This article's title is "Depth perception", but is is about depth perception only via vision. Yet we know that people can perceive the three-dimensionality of the world from senses other than vision. We can experience depth from stereophonic information from our two ears. We can close our eyes, and use our hands and bodies to feel our way around the world: haptics and kinesthesis. We could even block our eyes, ears, skin, and still tell when we are close to someone by smell, especially if he or she forgot to have a shower in the morning!

Can editors think of a more appropriate name for this article, or should these other sources of depth information be included?Robert P. O'Shea (talk) 16:57, 8 May 2008 (UTC)

Arguably, "Visual Depth Perception" would be a better title - but since most people understand "Depth Perception" to mean "Visual Depth Perception", we'd have to retain the present title as a redirect. If we ever get articles about other kinds of depth perception, then there would certainly be a case for a disambiguation page. Meanwhile, I don't see the need to change anything. SteveBaker (talk) 17:34, 19 May 2008 (UTC)

Wouldn't it be appropriate to have a section here on non-visual modes of depth perception, perhaps very brief, basically a list with links to little articles about each kind? I would also suggest that binocular vision should be identified here as the primary visual means of depth perception, since it's generally (and correctly) regarded as virtually a synonym — the other means of perceiving depth supplement or partially (and inadequately) substitute for binocular vision.Chelydra (talk) 19:01, 1 October 2008 (UTC)

Binocular vision is already first as a cue to depth perception in the text at the top of the article. It does not need to be rammed down peoples throats. As to putting in a section about non-visual cues for depth perception that sounds a reasonable idea to me. Dmcq (talk) 19:34, 1 October 2008 (UTC)

The ET counterpoint: Monocular Cues wide eyed animals and motion parallax .

Currently reads: "Some animals that lack binocular vision due to wide placement of the eyes employ parallax more explicitly than humans for depth cueing (e.g. some types of birds, which bob their heads to achieve motion parallax, and squirrels, which move in lines orthogonal to an object of interest to do the same)."

This should not refer to wide placement of eyes, right? Wide placement isn't the issue, the issue is whether the animal can see the field of vision, or the relevant parts of it, with both eyes, correct? So the issue is that, whether the image is not binocular due to obstructions like the nose or due to eye placement being so many degrees removed or a narrow field of view.

Should this be changed?

As a counter example I'll give you ET vs a piggeon. ET's eyes are wide man, but that dude sees binocular (don't even claim that he doesn't- blasphemy) while the pidgeon's eyes are close but they presumably don't.

ET shows us the error of our ways.--Δζ (talk) 03:41, 29 November 2008 (UTC)

Perhaps the original editor meant side placement rather than wide placement, but yes it's just wrong at the moment. Why not have a go at editing it, after all that's what wiki's about. Dmcq (talk) 13:13, 29 November 2008 (UTC)

Inferred Cues

Their physical position is noted, and SEEN very accurately in the mental stereo visualization process, though visible to only one of the 2 eyes in use.

This sentence is wierd, and the capslocked SEEN is distracting. It gives the appearance of hand waving, where the person is adding strength to their arguments by saying it more forcefully —Preceding unsigned comment added by 129.15.139.229 (talk) 14:51, 10 March 2009 (UTC)

New findings

Recemtly some scientists identified special cells on the retina that recognize onward motion - object coming towards the observer.

--Genezistan (talk) 18:59, 1 January 2010 (UTC)

Can animals "perceive" depth?

I have deleted the following from the introduction:

Although any animal capable of moving around its environment must be able to sense the distance of objects in that environment, the term perception is reserved for humans, who are, as far as is known, the only beings that can tell each other about their experiences of distances.

While this has been written and published, the most cursory search of the scientific literature finds plenty of references to perception of depth by animals (nearly 9000 Google hits for <depth perception chimpanzee>; "Depth perception in the rat [Rattus Norvegicus]"; "DEPTH PERCEPTION OF THE SYRIAN HAMSTER", etc. etc. And etc.) So it's at best an opinion, not an uncontroversial statement of fact.Pol098 (talk) 14:04, 5 January 2010 (UTC)

Evolution

CITATIONS VERY MUCH NEEDED. Danke. —Preceding unsigned comment added by 60.48.119.42 (talk) 07:10, 19 April 2011 (UTC)

I have added an Unreferenced section tag to the section so people notice it is missing citations and hopefully add them. If you can do that yourself please do so - just copy the format of some other citation in the article, it doesn't have to be wonderful - somebody else will fix up problems if the content is there. Dmcq (talk) 16:20, 19 April 2011 (UTC)

Do we really see the world in 2D, rather than 3D

Is this true? I've read this before. Is it true? 209.86.226.34 (talk) 22:39, 18 March 2012 (UTC)

Well, "seeing" is a multi-stage process. As explained in the intro, each eye receives a two-dimensional pattern of incoming light. The brain subconsciously combines the two patterns and uses both the binocular cues (differences in what the two eyes see) and monocular cues (lighting, motion, etc.) to reconstruct a three-dimensional representation of the world which is fed to the conscious mind. Certain optical illusions can fool the reconstruction process into creating an incorrect 3D representation. So, no, it's not 3D like a radar system is 3D, but it's also not 2D like a TV camera. -- Beland (talk) 17:53, 27 July 2016 (UTC)

Kinetic depth

I have added a paragraph about the kinetic depth effect, an important depth cue that has been extensively studied over the past 60 years, and I have provided citations and a link to the WP article on the same topic. However, in the preceeding section, Depth from motion, an entirely different phenomenon, having to do with calculating the time-to-contact of an approaching object, is described and given the potentially confusing name kinetic depth perception. This paragraph was added on May 29, 2007 by an IP editor who has made no contributions to this or any other page since, and no citation is given for the use of the term kinetic depth perception – in fact, the whole section lacks any citation.

"Kinetic depth perception" does not appear to be a term commonly used in the context of linear movement of an approaching object. A Google search on the phrase turns up only a few instances in which the term is used in this sense, and those appear to be mirror sites or sites influenced by this WP article. Otherise, all of the Google hits refer to the kinetic depth effect, even when the word "perception" is used (e.g. Kontsevich 1998) In any case, the phenomenon described is actually a cue to velocity, rather than depth: it is the same cue used by a baseball player in attempting to estimate the speed of a pitch. It is a perfectly valid phenomenon, but it may be out of place in an article on depth perception.

For the moment, I have added a sentence to distinguish this cue from the kinetic depth effect. I am wondering whether (1) to delete the section dealing with calculating approach time of a distant object, on the grounds that it lacks citations and is not really a depth cue, or (2) to rewrite that section using a different name for the phenomenon, or (3) to leave everything as it is.

I would be glad for suggestions from readers of this page. Brazzit (talk) 23:21, 24 June 2013 (UTC)

I would be inclined to support option (2), even if only to clarify that it may seem like a depth cue, but isn't. That way the information isn't completely lost, but doesn't mislead readers either :) --Waldir ^talk 11:38, 25 June 2013 (UTC)

Hearing no objection, I have rewritten the section using a term from the literature – "depth from optical expansion" and have provided citations. Brazzit (talk) 23:34, 5 July 2013 (UTC)

Relative size redirect

this page is a redirect from relative size. However, the subject matter is subjective, and I was hoping to find a comparison of sizes of things (molecules, macromolecules, cells, etc.) which are at very small scales. This seems like it might contribute more to the subject matter of the units page for measurement of length/distance.

tl;dr the redirect is not quite right but I don't have a solution at this moment. — Preceding unsigned comment added by RotogenRay (talk • contribs) 01:43, 18 June 2014 (UTC)

The redirect from "relative size" is there because that term is the usual name for one of the cues that the perceptual system uses to construct the psychological experience of three-dimensionality – which is, as you note, a subjective phenomenon. If "relative size" is also commonly used to refer to physical scales of measurement, perhaps there should be a disambiguation page for that term. Brazzit (talk) 21:42, 18 June 2014 (UTC)

Stereopsis is not a cue, is it?

I was wondering if in this part of the description...

Binocular cues include stereopsis, eye convergence, disparity,

According to the term description, stereopsis refers to the 3D perception process. So, while it uses cues like disparity, it is not a cue in itself. — Preceding unsigned comment added by 195.50.169.234 (talk) 12:44, 3 July 2015 (UTC)

In animals

I came to this article looking for a list of animals (or families of animals or whatever) that have this ability. I heard that the mantis is the only type of insect that does, and according to the article apparently some mammals do and some don't. Anyway, it would be interesting to add whatever is known. -- Beland (talk) 17:56, 27 July 2016 (UTC)

Vandalism

This article was vandalized a few months ago, but this vandalism was not corrected until today. Should this article be semi-protected to prevent this vandalism from recurring? Jarble (talk) 08:48, 6 January 2019 (UTC)