Questions tagged [vision]

Questions regarding how the brain interprets information from the eyes. Consider using the "eyes" tag for discussion of eye anatomy, physiology and evolution.

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Why does there have to be two muscles to control the size of the pupil?

In dim light, the circular muscles relax and radial muscles contract to allow more light to enter the eye, and vice versa in bright light. Why is there the need to have two muscles when probably the ...
1 vote
0 answers
55 views

Confused About Why Red Queen Hypothesis Wouldn't Apply to Deer's Color Vision [duplicate]

In this site,https://www.livescience.com/why-are-tigers-orange, it says ""But there seems to be no evolutionary pressure, particularly for deer, which are the main prey of the tiger, to ...
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Why do people say that blue light is damaging to the eyes?

It's easy to find claims that blue light (e.g., from computer screens) is damaging to the eyes. For example, here is some discussion of the topic. Is there any physical mechanism by which blue (not ...
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5 votes
1 answer
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Biological basis for the illusion of being pulled uphill on a *magnetic hill* when, in fact, one is coasting downhill?

A "gravity hill" is one where a downhill slope appears to be uphill, such that an object such as a car will appear to roll uphill when in fact it is moving downhill. This is described in a ...
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Optic Nerve: neurons/area and bit rate?

Does anyone know the number of neurons adjoining a cross sectional area of the optic nerve and the theoretical bit rate of the nerve? I read that the ON cross sectional radius is 3-5 mm and the ...
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Vision System: neural activity is modulated using FSK?

I’m learning about the human vision system and signaling. Does anyone know if the signaling used by the vision system is modulated at the neuron using amplitude frequency shift keying? I present my ...
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2 votes
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Vision and signal through the nervous system? [closed]

I have questions regarding the signal path between the retina and other parts of the brain. An understanding and then questions in bold follow. Wikipedia states: Retinal ganglion cells spontaneously ...
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-1 votes
1 answer
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How does the brain activate retinal cones in darkness?

The activation of retinal cones by light is how vision is formed; yet there are other methods, such as mechanical one, for activating light, such as pressure photopsia/phosphenes. This occurs when ...
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Why do eyes feel exhausted after reading on a computer screen for a long time? [duplicate]

Similar question before closing this one was: Question. The answer holds true for most of the observations, but my observation differs from what is described in that question. Even if we consider that ...
25 votes
2 answers
4k views

Why do blood vessels in the eye not obstruct vision?

As light enters the eye, it reaches the photoreceptors at the "base" of the retina, which then pass that signal to the bipolar and ganglionic neurons -- the latter of which send the signal ...
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2 answers
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Are color-blind carriers partially colorblind?

Since color-blindness passes along an recessive gene in the X-chromosome, women are rarely affected, while men are affected more frequently. Women with one copy of the color-blindness gene are said to ...
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7 votes
1 answer
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Do color-blind people have more rod cells in their retinae than the normally sighted?

All types of color-blindness are said to be caused by the defect or lack of cone cells in the eyes[1]. Since cone cells sense color[2] and rod cells can only sense light intensity[3], the lack of cone ...
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6 votes
1 answer
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How is the extraordinary eyesight of some deep-sea creatures explained?

Mantis shrimp is a marine crustacean that is known to have a vision system that is much more complex than the eyes of many animals living on the ground. As explained here, it has 12 types of ...
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7 votes
1 answer
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What do cats see when they look at 2D, still images?

My cat doesn't like other cats. She doesn't really like anyone that isn't part of our family. So when she sees other cats she will aggressively try and chase them out of her area. She will also do the ...
1 vote
1 answer
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How does slowed action potential propagation in the optic nerve cause blurred vision?

Multiple sclerosis is accompanied by optic neuritis, and there is demyelination of the optic nerve, causing the action potential to be propagated more slowly along axons. But how does this lead to ...
0 votes
2 answers
91 views

Would green light look different if blue and red cones were deactivated

When looking at a graph plotting "blue", "green" and "red" cones reponses to different wavelengths, you can see that any wavelength trigerring a response from green cones ...
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1 vote
1 answer
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Why do I see purple stripes when moving a small source of light (flashlight) quickly in a dark room?

I was playing with my phone's flashlight (white) in a dark room, Just moving it around quickly when I noticed that I could see thin stripes of purple in the same shape as my hand moved, they didn't ...
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Permission for Figure Reuse

I was wondering how I can go about gaining permission for reuse of a figure in this post. I was hoping to reuse the image that is exemplifying the cross section of the retina. If anyone know please ...
1 vote
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Do animals with very small eyes see microscopic objects?

I understand that many small creatures have very elementary eyes: they are not scaled-down versions of the human eye but as I understand it often just light-sensitive organs for detecting movement. ...
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2 votes
1 answer
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Is chromatic aberration related to the spectral sensitivity of the human eye and can it cause "relative myopia" and "relative farsightedness"?

in the text below, the authors equate chromatic aberration and the spectral sensitivity of the human eye. Aren't these two very different phenomena though? They also propose a so-called "relative ...
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44 votes
3 answers
14k views

Are humans more adapted to "light mode" or "dark mode"?

I was discussing with a colleague about using dark-mode vs. light mode and remembered an article arguing that humans vision is more adapted to light-mode rather than dark-mode: I know that the trend “...
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1 vote
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Which animals can see (or feel) the Moon’s infrared radiation?

The luminosity (bolometric) of the Moon in infrared is several times greater that its luminosity in visible light. Moreover, it may be rather possible for the Moon to be obscured by some fog or haze ...
2 votes
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Eye Optics/Emmert's law: Where to place scaled copies of an object so they have identical images on the retina?

I read that the center of projection of the human eye is the entrance pupil. So given a light ray which intersects the objects position and the center of the aperture stop, all copies of said object ...
3 votes
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Understanding David Chalmers claims on direct mappings between our vision and visual awareness systems

I am reading the popular 1995 paper "Facing Up to the Problem of Consciousness" by David Chalmers [PDF] as part of my philosophy course. I am only asking about the relevant vision related ...
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1 answer
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Term for a prey animal's recognition that something potentially threatening is looking at it?

On my daily walks I frequently see individual or small groups of cattle egrets. At first I would try to photograph them but they would fly away. This vexed me because they ignored everyone else ...
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1 answer
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How much percent of image does our eyes focus at any instant?

I learned in highschool that even thought we have a wide view, we only observe a tiny fraction of that view through our eyes. So at any instant we are not really looking at all the objects infront of ...
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2 votes
1 answer
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Why does our visible range not include infrared or UV radiation? [duplicate]

As the radiation peak of the sun is in the UV region and since at around room temperature materials emit radiation at IR, I wonder why our eyes are not capable of using these wavelengths. I guess ...
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1 vote
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Why do we get tunnel vision during fight or flight response?

I have a question regarding tunnel vision during the fight or flight response. I believe that during fight or flight high levels of adrenaline are released which causes the pupils to dilate allowing ...
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1 vote
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Why do we have both on and off bipolar cells?

I have a question regarding the reason behind the 2 bipolar cells. So, from my understanding we have both on and off bipolar cells and from the numerous diagrams I have seen, I find that most show a ...
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1 vote
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Why does Cyan appear bluish rather than greenish, when the phototopic eye sensitivity is highest in green (and Cyan contains blue and green equally)?

Cyan contains blue and green equally. Phototopic eye sensitivity is highest in green. Why, then, does Cyan appear bluish to most of us, rather than greenish?
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1 answer
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What is the smallest visual unit perceptible to the human eye, like a pixel? (esp. in visual static)

If you close your eyes, you can often see visual static, where individual pixel-like things are much more visible than with the more smooth, crisp images one gets with open eyes. This led me to wonder ...
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How does the human eye generate spikes?

Disclaimer: I have an academic background in computer vision but not biological vision. Background: Classical computer vision is concerned with images from cameras that have a fixed exposure time for ...
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2 votes
2 answers
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Is Brain Eye connections reversed in all animals or just Humans?

I know that Brain Eye connections are reversed in Humans, Left Hemisphere controls the Right eye/Right side of the body Right Hemisphere Controls the Left eye/Left side of the body Is it true in ...
5 votes
1 answer
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Vitamin A Deficiency

I have a quick question regarding Vitamin A deficiency. The photoreceptor molecules in both rods and cones have the same general structure which is retinal which is bound to a protein called opsin ...
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3 votes
1 answer
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Visual receptive fields

What I know about centre-surround type receptive fields is that depending on whether the region is on or off, the response to being stimulated is either excitatory or inhibitory respectively. So if a ...
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5 votes
1 answer
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Why did we lose our fourth type of cone cell (in the eye)?

Most species of birds, reptiles and fish have four types of cone cells in their retina, thus they have four independent channels for conveying color information. They are: short-wave (S) cones: ...
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0 votes
1 answer
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Does opponent process happen in the retina or in the brain?

I understand that both the Trichromatic Process and the Opponent Process take place in human vision. Trichromatic Process is widely accepted to happen in the retina, however I heard differing accounts ...
1 vote
2 answers
114 views

How do big cats perceive objects, specifically vehicles?

Right so we have been on safari in South Africa recently and before encountering big cats (lions) we have been told to hold still and not reach out beyond the boundaries of our safari vehicle because ...
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2 votes
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Does the human eye see things at twice the distance in a mirror?

If I'm standing 3ft away from a mirror and looking at something in it that is behind me but 5ft away from the mirror, do my eyes see that object as 3ft? Or 8?
1 vote
1 answer
226 views

Why are eyes more sensitive to flicker in periphery — contradictory answers

In terms of the perception of flickering by CRT monitors, This answer suggests that peripheral vision has faster response and is thus more sensitive to flicker due to being provided by rod cells. ...
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2 votes
1 answer
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How are the images of both eyes combined to form one image?

When you see an object by one eye, ex.right eye, you see it from the right direction and the opposite if you see it by your left eye, but when you open both eyes, the image appears somehow centric in ...
2 votes
1 answer
112 views

Vision: what is the difference between on-off ganglion cells and lateral inhibition?

Is 'lateral inhibition' just a term for the biological basis of the functioning of the on-center (or off-center) ganglion cells? Or do these terms describe separate processes?
1 vote
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Is it possible to simulate tetrachromatic vision in a trichromat?

Suppose we are able to stimulate the whole matrix of cones of a human retina, targeting each cone individually¹. Normally we would project an image in the LMS color space onto the cones, in such a way ...
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5 votes
1 answer
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Predatory animal tracking methods

As far as I know, humans are the only animals that use visual references to track prey that is not immediately visible to them. Do any other animals do this? I'm not referring to stalking prey ...
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How far can a human see at night?

I am not talking about seeing in total darkness, which I understand is not possible. I am looking more about a question how far can a human see during starry night or with half moon/full moon. I tried ...
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2 votes
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Do pale skinned people show other low light adaptations?

So, pale skin is, fundamentally, an adaptation to living in low light conditions. Pros: reduce energy spent on producing melanin, increase vitamin D production. Cons: more vulnerable to sunburns and ...
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3 votes
1 answer
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Comparion between machine vision & human vision

I hope this is the correct Stackexchange to ask this question. I am trying to know : What is the current status of knowledge regarding human vision and pattern recognition. More specifically, How ...
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Farsightedness and the eye

When a farsighted person looks at a distant object and sees it clearly, what is the state of their eye lens? Is it relaxed? Rationale: It is something we read about in class that is confusing.I know ...
5 votes
2 answers
289 views

Understanding the "Waterfall Illusion"

Motion after-effect illusions, such as the waterfall illusion, refer to illusions where fixating a screen which shows stimuli moving in a particular direction elicits the perception of motion in the ...
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Is there benefit of use of red light over dim white light when interacting with rodents in the dark phase?

I've come across some "percieved wisdom" that rats and mice do not "see" red visible light and so use of this wavelength will allow humans to interact with rats in their active nocturnal phase without ...
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