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Tetrachromacy is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye. Organisms with tetrachromacy are called tetrachromats.

The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet.
Tetrachromacy is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye. Organisms with tetrachromacy are called tetrachromats.

In tetrachromatic organisms, the sensory color space is four-dimensional, meaning that to match the sensory effect of arbitrarily chosen spectra of light within their visible spectrum requires mixtures of at least four primary colors.

Tetrachromacy is demonstrated among several species of bird, fish, amphibian, reptile, insect and some mammals. It was the normal condition of most mammals in the past; a genetic change made the majority of species of this class eventually lose two of their four cones.

From Wikipedia, the free encyclopedia

Physiology
The normal explanation of tetrachromacy is that the organism's retina contains four types of higher-intensity light receptor (called cone cells in vertebrates as opposed to rod cells, which are lower-intensity light receptors) with different absorption spectra. This means that the organism may see wave-lengths beyond those of a typical human's vision, and may be able to distinguish between colors that, to a normal human, appear to be identical. Species with tetrachromatic color vision may have an unknown physiological advantage over rival species.

Birds
Some species of birds, such as the zebra finch and the Columbidae, use the ultraviolet wave-length 300–400 nm specific to tetrachromatic color vision as a tool during mate selection and foraging. When selecting for mates, ultraviolet plumage and skin coloration show a high level of selection. A typical bird eye will respond to wave-lengths from about 300 to 700 nm. In terms of frequency, this corresponds to a band in the vicinity of 430–1000 THz. Most birds have retinas with four spectral types of cone cell that are believed to mediate tetrachromatic color vision. Bird color vision is further improved by the filtering of pigmented oil droplets that are located in the photoreceptors. The oil droplets filter incident light before it reaches the visual pigment in outer segments of the photoreceptors.

The four cone types, and the specialization of pigmented oil droplets, give birds better color vision than that of humans . However, more recent research has suggested that tetrachromacy in birds only provide birds with a larger visual spectrum than that in humans (humans cannot see ultraviolet light, 300-400 nm), while the spectral resolution (the "sensitivity" to nuances) is similar.

Insects
Foraging insects can see wave-lengths that flowers reflect (ranging from 300 nm to 700 nm. Pollination being a mutualistic relationship, foraging insects and some plants have coevolved, both increasing wave-length range: in perception (pollinators), in reflection and variation (flower colors). Directional selection has led plants to display increasingly diverse amounts of color variations extending into the ultraviolet color scale, thus attracting higher levels of pollinators.

From Wikipedia, the free encyclopedia

Mammals

Reindeer
In areas where reindeer live, the sun remains very low in the sky for long periods. This means the light is scattered such that the majority of light that reaches objects is blue or U.V. Some parts of the environment absorb U.V. light and therefore to U.V.-sensitive reindeer, appear to be black, strongly contrasting with the snow. These include urine (indicating predators or competitors), lichens (a food source) and fur (as possessed by wolves, predators of reindeer). Although reindeer do not possess a specific UV opsin, retinal responses to 330 nm have been recorded, mediated by other opsins. It has been proposed that UV flashes on power lines are responsible for reindeer avoiding these structures because "...in darkness these animals [reindeer] see power lines not as dim, passive structures but, rather, as lines of flickering light stretching across the terrain."

Humans
Apes (including humans) and Old World monkeys normally have three types of cone cell and are therefore trichromats. However, at low light intensities, the rod cells may contribute to color vision, giving a small region of tetrachromacy in the color space; human rod cells' sensitivity is greatest at a bluish-green wave-length.

In humans, two cone cell pigment genes are present on the X chromosome: the classical type 2 opsin genes OPN1MW and OPN1MW2. People with two X chromosomes could possess multiple cone cell pigments, perhaps born as full tetrachromats who have four simultaneously functioning kinds of cone cell, each type with a specific pattern of responsiveness to different wave-lengths of light in the range of the visible spectrum. One study suggested that 2–3% of the world's women might have the type of fourth cone whose sensitivity peak is between the standard red and green cones, giving, theoretically, a significant increase in color differentiation. Another study suggests that as many as 50% of women and 8% of men may have four photopigments and corresponding increased chromatic discrimination compared to trichromats. In 2010, after twenty years of study of women with four types of cones (non-functional tetrachromats), neuroscientist Dr. Gabriele Jordan identified a woman (subject cDa29) who could detect a greater variety of colors than trichromats could, corresponding with a functional tetrachromat (or true tetrachromat).

Variation in cone pigment genes is wide-spread in most human populations, but the most prevalent and pronounced tetrachromacy would derive from female carriers of major red/green pigment anomalies, usually classed as forms of "color blindness" (protanomaly or deuteranomaly). The biological basis for this phenomenon is X-inactivation of heterozygotic alleles for retinal pigment genes, which is the same mechanism that gives the majority of female new-world monkeys trichromatic vision.

In humans, preliminary visual processing occurs in the neurons of the retina. It is not known how these nerves would respond to a new color channel, that is, whether they could handle it separately or just combine it in with an existing channel. Visual information leaves the eye by way of the optic nerve; it is not known whether the optic nerve has the spare capacity to handle a new color channel. A variety of final image processing takes place in the brain; it is not known how the various areas of the brain would respond if presented with a new color channel.

Mice, which normally have only two cone pigments, can be engineered to express a third cone pigment, and appear to demonstrate increased chromatic discrimination, arguing against some of these obstacles; however, the original publication's claims about plasticity in the optic nerve have also been disputed.

Humans cannot see ultraviolet light directly because the lens of the eye blocks most light in the wavelength range of 300–400 nm; shorter wavelengths are blocked by the cornea. The photoreceptor cells of the retina are sensitive to near ultraviolet light, and people lacking a lens (a condition known as aphakia) see near ultraviolet light (down to 300 nm) as whitish blue, or for some wavelengths, whitish violet, probably because all three types of cones are roughly equally sensitive to ultraviolet light; however, blue cone cells are slightly more sensitive.

Tetrachromacy may also enhance vision in dim lighting, or when looking at a screen.

WendyDarling wrote:I studied university level arts and I am a tetrachomatic which makes me wonder if that is one aspect of my abilities that drew me into the arts so because of being tectrachromatic I was compelled to study art.

Maia wrote:Sadly, no.

MagsJ wrote:

Maia wrote:Sadly, no.

..can one miss what one doesn't know of?

I'm surprised that Science hasn't yet found the ability to wire a person up to a 'visual maker' i.e. artificial vision generator.. or have they?

Where is Science when we need it most.. inventing new and improved ways to dis-able us into docility and submission, so the peasants can never revolt again.

Maia wrote:Those who are born completely blind never have their visual cortex stimulated, so it atrophies and, it is reckoned, most of its processing power (which is actually quite big, since vision is very complicated) is given over to other functions. In other words, it is not possible to "wire a person up". On the other hand, for those who lose their sight later in life there is every chance of success, and much has already been done.

But to answer your first point, no, of course not. I do not consider my life deficient in any way.

MagsJ wrote:

Maia wrote:Those who are born completely blind never have their visual cortex stimulated, so it atrophies and, it is reckoned, most of its processing power (which is actually quite big, since vision is very complicated) is given over to other functions. In other words, it is not possible to "wire a person up". On the other hand, for those who lose their sight later in life there is every chance of success, and much has already been done.

But to answer your first point, no, of course not. I do not consider my life deficient in any way.

I did not imply a deficiency in you at all, but posed an empirical inquiry on 'the absence of loss', which in my mind implies that the unexperienced cannot be fully-imagined and cannot therefore be manifested into a 'feeling/feelings', so you will never have that feeling of loss.. I am not sure which is preferable?

Do you think you have acquired other senses beyond the ones we know as verifiable?

Maia wrote:It's certainly true that I can't imagine what vision is like, much as I've tried. But not in a sad or bitter sort of way, but rather, one of insatiable curiosity.

If you mean a psychic sense, I believe I once had a prophetic dream, which I've mentioned before. I sometimes hear things, voices and such, that aren't there, especially when waking up. So in other words, they could be part of a dream.

But if you're talking about actual physical senses, I have very good echo location, as do many people born blind. If I click my tongue rapidly I can tell the size of a room I'm in, or if I'm outside, large objects up to about 30 feet away. This doesn't work if I have a cold though, so I tend to bump into things a lot more.

MagsJ wrote:

Maia wrote:It's certainly true that I can't imagine what vision is like, much as I've tried. But not in a sad or bitter sort of way, but rather, one of insatiable curiosity.

Sounds akin to unrequited love, from your above premise.. think of that feeling, then apply it to those thoughts.. it could start triggering your imagination to 'go there' as I think the imagination is borne of thought and feeling.

If you mean a psychic sense, I believe I once had a prophetic dream, which I've mentioned before. I sometimes hear things, voices and such, that aren't there, especially when waking up. So in other words, they could be part of a dream.

I'll have to revisit that thread, and get back to you here on it, as I do not recall what your dream was about.

But if you're talking about actual physical senses, I have very good echo location, as do many people born blind. If I click my tongue rapidly I can tell the size of a room I'm in, or if I'm outside, large objects up to about 30 feet away. This doesn't work if I have a cold though, so I tend to bump into things a lot more.

..a skill acquired from a young age, or honed over many years?

MagsJ wrote:Oh yes, I do recall your dream recount.. such occurrences stick with us for life, as they're not your everyday folly, and so become ingrained in the psyche.. seared into a part of mind, by a biochemical branding iron of sorts. Who knows what premonitions are borne of.

So, an instinct kicked in? borne from a need, it seems.. were you very young/a toddler, when it started to manifest?

Maia wrote:I'm sorry Mags I sort of derailed your thread. Tetrachromacy is actually really interesting, as is anything to do with visual perception. Can you explain to me, in a way that I might understand, what the difference is between that and normal sight? Yes, I agree it's a bit of a challenge.

MagsJ wrote:

Maia wrote:I'm sorry Mags I sort of derailed your thread. Tetrachromacy is actually really interesting, as is anything to do with visual perception. Can you explain to me, in a way that I might understand, what the difference is between that and normal sight? Yes, I agree it's a bit of a challenge.

Tetrachromats see over 9+ million more colours than those who aren't tetrachromats, which enables the tetrachromat to see colours within the colour of an object (where others would only see that one colour) due to having an extra/4th cone that causes the phenomenon, which is caused by a genetic mutation.. mainly in females.

Colours pop out at you, and sometimes swirl across the object, which is quite a psychedelic experience because of that. I have no idea what use it has in humans, but it has a mesmerising effect, as the mind seems to be taken up with translating this multitude of colour variation within the object.

Maia wrote:Does this genetic mutation tend to come as a package with other genetic mutations and traits, as is so often the case? For all I know, I might even have it.

Tetrachromats

Women get two X chromosomes, one from their mother (XX) and one from their father (XY). They’re more likely to inherit the necessary gene mutation from both X chromosomes. Men only get one X chromosome. Their mutations usually result in anomalous trichromacy or color blindness. This means that either their M or L cones don’t perceive the right colors.

A mother or daughter of someone with anomalous trichromacy is most likely to be a tetrachromat. One of her X chromosomes may carry normal M and L genes. The other likely carries regular L genes as well as mutated L gene passed through a father or son with anomalous trichromacy.

One of these two X chromosomes is ultimately activated for the development of cone cells in the retina. This causes the retina to develop four types of cones cells because of the variety of different X genes passed on from both mother and father.

Maia wrote:Maybe we will never know if I have the gene, unless I have kids, which at this rate seems increasingly unlikely.

Urwrongx1000 wrote:

Maia wrote:Maybe we will never know if I have the gene, unless I have kids, which at this rate seems increasingly unlikely.

Nice pity card, aren't you a little young to give up on life already?