Thread: Some things you just simply cannot do?

Studies have shown that some women do possess a fourth photopigment cone. The controversy lies in whether or not their brains have developed the means of utilizing the cone correctly.

I assume you are getting your information from wikipedia - which isn't the most reliable source of up to date information. There was a study in the early 1990's that ran women through color testing, in it there was at least one who came out with results that only a tetrachromat could have achieved. - here I'll do a quick google search http://www.cs.utk.edu/~evers/documents/tetraChromat.txt : there are several of other articles out there


And as for the ability to differentiate between colors - thats all that seing new color is! How would you explain what the world looks like to somebody with a red/green deficiency? You couldn't! Those pigments(and the shades within) are totally foreign to them. By the same token, how would we percieve the colors that a tetrachromat sees as their fourth primary? We have no idea what the colors look like to them, because to us, they are just shades inbetween.

Originally Posted by archdreamer

Human tetrachromacy has yet to be verified, but if it occurs, it would not allow tetrachromats to see colors 'outside' of the usual spectrum, but would simply increase their ability to differentiate between colors that a normal human may perceive as identical.

I considered this when I went to sleep last night. I could be totally off on this I've done no research but if indeed there was a fourth primary color, then two colors that looked identical to me could look quite different a so called "tetrachromat" if they contained different saturations of the fourth pigment that I cannot discern. Even in the RGB color space there are infinite possibilities; you could have saturation values in the decimal places out to infinity. Can the human eye discern the difference between Red with a saturation of 155 and red with a saturation of 155.000000000000000000000000001? Probably not, but the difference would be there. Adding a fourth primary would certainly change the color space for those able to perceive it, and they would be able to discern more colors, but there wouldn't really be more per se.

Originally Posted by poliganometry

Studies have shown that some women do possess a fourth photopigment cone. The controversy lies in whether or not their brains have developed the means of utilizing the cone correctly.

I assume you are getting your information from wikipedia - which isn't the most reliable source of up to date information. There was a study in the early 1990's that ran women through color testing, in it there was at least one who came out with results that only a tetrachromat could have achieved. - here I'll do a quick google search http://www.cs.utk.edu/~evers/documents/tetraChromat.txt : there are several of other articles out there


And as for the ability to differentiate between colors - thats all that seing new color is! How would you explain what the world looks like to somebody with a red/green deficiency? You couldn't! Those pigments(and the shades within) are totally foreign to them. By the same token, how would we percieve the colors that a tetrachromat sees as their fourth primary? We have no idea what the colors look like to them, because to us, they are just shades inbetween.

My question is, and I really should research this before running my mouth (I honestly usually do, but I'm in a hurry at the moment lol), scanning the eyes of a suspected perceiver of a fourth primary is one thing, developing a real world test... another. An objective test would be necessary not to prove the receptors were there, but functional. I would imagine a test like the ones that we already use to determine colorblindness. But wouldn't one have to already be a tetrachromat in order to develop such a test? I can't mix an image to where it has a letter "hidden" by printing it in the fourth primary color if I can't already discern that color to manipulate it can I? Lastly, and this applies to the making a new color in your dreams as well, and mentioned above, how would you quantify it if you did? If I indeed create a new color in a dream, I can't imagine describing it! Obviously you couldn't be like "Well it's kinda like a mixture of red and cerulean" Yeah that would be in the RGB color space and not "invented" at all. So even if some of us did succeed in dreaming up a color, could we ever really explain it? I wonder.

Big edit Okay I went and read your cited article like I SHOULD HAVE to begin with. The colored lights test is intriguing, still it's not scientifically rock solid in my mind.

I would normally say when I'm being chased I can never run away, but last night I was able to run away when I was being chased although the chasers were faster than me. I can always run, but my running in a dream was like someone else trying to walk slowly. Until last night that is.

I've noticed that in my dreams, including my lucid ones, the more "urgently" I'm trying to do something, the more exponentially ineffective it will be. For example, running madly through a field with no purpose? Easy. Running at any decent speed when fleeing a large, angry, dreambeast? Not so easy.

Originally Posted by poliganometry

Studies have shown that some women do possess a fourth photopigment cone. The controversy lies in whether or not their brains have developed the means of utilizing the cone correctly.

I agree. I am using the term 'tetrachromat' in the same sense as Jameson et al.

Originally Posted by Jameson et al

Note that trichromacy is a composite system that, when maximized,
consists of the output of three retinal photopigment classes fed
into three separate neurophysiological color channels. Individuals with
four-photopigment retinas would function as trichromats if, during the
process of producing sensations, the visual system reduced the input
from the four-photopigment classes into a three-channel system. This
four-photopigment/three-channel model has generally been the accepted
theory among vision researchers as the most plausible theory for four
photopigment retinal processing (MacLeod, 1985; Miyahara, Pokorny,
Smith, Baron, & Baron, 1998; Nagy et al., 1981; M. Neitz & J. Neitz,
1998). The term tetrachromat implies an extension of the three-channel
system and is appropriate only for four-photopigment individuals if it
were demonstrated that their retinas with four-photopigment classes
were feeding into a greater-than-three-channel system and producing a
higher dimensional perceptual experience, relative to the trichromat
percept. Until such a higher dimensional percept is demonstrated, only
the term four-photopigment individuals is warranted for individuals
with a four-photopigment class retinal phenotype.

Although there is considerable evidence that females with this genetic trait do percieve color differently, I have yet to see conclusive evidence that tetrachromacy in the sense above occurs in humans. If there is more recent confirmation of tetrachromacy in this sense, then please link, because it's pretty interesting.

And as for the ability to differentiate between colors - thats all that seing new color is!

Without getting into a debate about qualia and what does or does not constitute a novel color, suffice to say that by 'outside', I meant 'outside the frequency range of typically visible light'.

For those interested in the color vision of humans with four photopigment cones, the sources I'm going by are:

http://www.klab.caltech.edu/cns186/papers/Jameson01.pdf - Jameson paper
http://vision.psychol.cam.ac.uk/jdmo...n_Carriers.pdf - Jordan paper


EDIT:

As an unrelated note, I sometimes notice that each of my eyes perceives color slightly differently. A trick of lighting?

Hey, me too. My right eye always seems to perceive richer color, while my left eye has better night vision. I always assumed that this was due to differing ratios of rod and cone photoreceptors in my eyes, but I never really researched it. Anyone know?

EDIT AGAIN: We seemed to have hijacked the thread. If anyone wishes to discuss this further, might I suggest we move to a new thread in the Lounge, and link to it from here?