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Old December 22nd, 2017, 12:31 PM
Doug Kerr Doug Kerr is online now
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Join Date: May 2006
Location: Alamogordo, New Mexico, USA
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Hi, Jerome,
Quote:
Originally Posted by Jerome Marot View Post
Now we are talking.

<quoted passage lost by the forum software>

That is not quite true and the answer lies in our genes and the way the human visual system functions.

For some part of the human visual system, the function depends on many genes and, possibly, on external factors. Take for example the way humans see at night (an understudied feature of our vision system, but I digress...): our ability to increase sensitivity to light in the rods depends on the availability of rhodopsin, which is derived from vitamin A. Here, two humans will exhibit different ability depending on their diet (and plenty of other things).

But human colour sensitivity depends on very few genes. Actually, out ability to discern colours depends on 3 pigments and each one is encoded on a single gene. The spectral sensitivity of a single cone cell directly depends on the type of molecule that cone uses as a pigment. In turn, each pigment is encoded on a single gene. Therefore, to have different spectral sensitivity one needs different genetics: mutation.

As a consequence, if we consider non-mutant humans (and we must exclude mutations, because most mutations actually make humans more colour-blind), the maximal capacity of differentiating between colours is given by the pigments, which are fixed by genetics. Some people will have poorer abilities, because they are untrained or have poor vision, etc... but nobody can actually see more colours than the pigments can discern.
All well said, and indeed I took the liberty of oversimplifying the topic.

Thanks for that contribution.

Best regards,

Doug
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