Re: Quest for colours: what's basic then?

>> White is an epitome of purity in all cultures.
>
>Wow.
>
>So, somebody did a study of ALL CULTURES and determined that, in each of
>those cultures, the "epitome of purity" meme was both present and
>associated with the color white.
>
>Must've been a DARPA grant.
Can you name a single culture where this does not hold?

A nihilist stance like the one you are displaying, merely
negating without providing any proof or argument to
contradict mine, leads us nowhere.

My argument and proof is: I know of no culture where the
equation white=purity does not hold. It is very simple
for you to refute this: just provide a contradictory
example. Until you have provided an example to the
contrary, the equation holds as a reasonable universal.
The argument that "there could be some unknown culture
where the equation does not hold, and thus it does not
hold" is pure speculation. Following that line of
reasoning, I could say: "It is not true that all peoples
have a language, because there _might_ be some undiscovered
people somewhere who doesn't have a language; I haven't
found any languageless people yet, but you know, who
knows what is lurking there in the unknown?, therefore
you cannot consider language as a universal feature
of peoples".

Also, when one talks about "universals", one talks
simply about general trends that are useful because
they are known to be valid for a majority of elements.
There is no attempt to arrive at absolute truths that
are indisputably true for any existing, possible or
imaginable element, because proving such an absolute
truth is simply impracticable outside the abstract realm
of mathematics. So your insistence in that there has
been no experiment that proves that some universal
trend is truly valid for an absolute _all_ is simply
pointless.


>> When trying to understand the working of human vision,
>> one has to keep in mind that the cone receptors are just
>> the beginning of the story and that the tri-stimulus
>> signal that is generated by them is then processed through
>> a neuronal network that results in an _perceptual_ space
>> organized into three axes: the luminance axis (with
>> white and black at the extremes) and two hue axes (the
>> red-versus-green and the yellow-versus-blue ones). It is
>> these six basic percepts what form the actual building
>> blocks of our colour experience, and not the three kinds
>> of cones, which merely define the tri-stimulus signal
>> space that is useful for prompting retinal responses by
>> mixing lighwaves, retinal responses that only when
>> further processed by our visual neuronal network generate
>> in our minds the perception of the intended colours.
>
>
>So, why do people perceive GREEN as BLUE+YELLOW?
Hold it. People do not _perceive_ green as blue+yellow.
I cannot perceive any trace of blue percept or yellow
percept in a pure green, while I perfectly detect the
presence of those percepts in turquoise and chartreuse.
People who have actually experienced the binary hue
that results from combining the blue and yellow percepts
have described the experience as seeing a colour they
had never seen before, and of course they had seen green
before. If you add green percept to yellow percept, you
will never get turquoise, because blue percept is lacking.
If green actually were blue+yellow, and therefore turquoise
were blue+yellow+more blue, you should be able to get
turquoise by mixing yellow with a lot of green, and you
should actually perceive some trace of yellowishness in
turquoise, but this simply does not happen.

People _learn_ that when mixing blue and yellow *paints*
you get green paint, and then this notion of green as a
"mixture" of blue and yellow gets reinforced by the fact
that several inherent features of green are midway between
those of blue and yellow (temperature, lightness) and by
the fact that green is less "far off" from its neighbors
yellow and blue than red is from its neighbor yellow
because green has a relatively low salience, so green seems
to 'fit' well as the colour to go _between_ yellow and blue.
That is, green displays a certain inherent *similarity* to
both blue and yellow that makes it appear as an appropriate
*transition* from yellow to blue, but that is different
from green being an actual blue+yellow mixture. Under normal
circumstances, the percepts blue and yellow simply are not
allowed to mix, because the blue/yellow opponent pathways
of the retinocortical neuronal network prevent their mixing.
The percept green, for its part, belongs to the red/green
opponent channel, which works independently of the
blue/yellow channel. The only known way to get blue and
yellow actually fused into the novel binary hue "yellowblue"
is by means of an optical illusion that is formed outside
the opponent pathways.

Cheers,
Javier

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