 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?
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