blue vs ...

[aroraborealis]

When we're feeling sad or down, we say we're feeling blue. What colors go with other moods? Happy? Tired? Excited? Angry? ... others?

Comments

[mzrowan.livejournal.com]

You can also be in a black mood, although then we get into the debate over whether black is a colour. ;-)

[mzrowan.livejournal.com]

Oh, and I think most people would understand roughly what you meant if you said, "I'm feeling grey," (which to me is best described as the stayed-up-all-night sketched-out kinda feeling).

[signsoflife.livejournal.com]

Well, "black" is a perception created in the brain by a certain pattern of cone stimulation (0, 0, 0), which can represent many different combinations of wavelengths of light and may vary from person to person and from animal to animal (e.g., a person without long-wavelength cones will perceive as black what a person with long-wavelength cones will perceive as deep red; a human will perceive as black what many birds will perceive as ultra-violet.)

The other possible interpretation of "black", as a complete absence of electro-magnetic radiation, just doesn't exist in this universe as far as I know.

So I'd say black's a color.

(I can't help it, I've been writing the color vision test this weekend and just finished reading up on UV perception in birds. . . )

[coraline]

<3

[dpolicar]

a human will perceive as black what many birds will perceive as ultra-violet

The more I think about this phrase, the less sure I am that I know what it means.

The closest I come is that many birds distinguish via UV perception among colors that humans perceive as black.

[signsoflife.livejournal.com]

Birds have a cone cell which is sensitive in the near-ultraviolet. So, yes, they can distinguish between wavelengths of light which humans would perceive as "black".

I'd be careful about saying they can distinguish *among* colors in the near-UV; with only one cone being triggered[1], they wouldn't be able to distinguish between a brighter, lower-wavelength stimulus and a dimmer, higher-wavelength stimulus.

For instance, given three surfaces, one of which reflects 370nm light, one reflects 330nm light, and one reflects, say, 80nm light[2], the human will perceive them all as black; the bird will perceive the first two as UV and the third as black; but the first two will be two intensities of the same color, because only the UV cone is operating at those short wavelengths.

Birds also use the UV cone in combination with others to perceive mixed colors, like humans do, but I'm not getting into that here.

[1] we know only one kind of cone's being triggered because birds' other cones overlap with human vision.

[2] the article I'm referring to as I make up these numbers actually cuts off the bottom of the chart for bird vision, so I picked 80nm out of the air as being way way low.

[moominmolly.livejournal.com]

I love your current reading list. I foresee it being extra fun to talk to you in the coming weeks.

[miss-chance.livejournal.com]

Since you asked, that made total sense to me, at least. It was just better phrased than I usually encounter it in texts written for lay-people such as myself.

Can I see your citations? They sound like really fun articles to read. Also, I'm curious, I've heard bits and snippets about some people, apparently more commonly women than men, being quad-cromats (if that's the right word) and having more sensitivity in the green/blue-green end of the spectrum. Is that part of your current reading? I'd love to find more good writing on that.

What does "I've been writing the color vision test..." mean? That is to say- you could mean you were writing a test for students to assess and evaluate their understanding of how color vision functions, or You could mean you were writing, oh, I don't know, a program that produces various wavelengths of light and measures responses to assess and evaluate the sensitivity in an individual or animal to various light-wavelength-stimulii. I'm curios- either would be cool.

[signsoflife.livejournal.com]

The article I'm using as a base for a lot of this is called "What Birds See", Scientific American July 2006 by Timothy Goldsmith. It's quite good.

Writing the test, in this instance, means writing questions for a midterm for undergrads.

Regarding "female tetrachromatism" -- the number of studies on it seems limited, but people who look for it seem to find it. Or, more specifically, it's a fact that some women have at least four photopigments; the actual question is whether that leads to better color discrimination. The foundational article seems to be Jameson, Highnote and Wasserman, 2001, Richer color experience in observers with multiple photopigment opsin genes, PSYCHONOMIC BULLETIN & REVIEW Issue 8 volume 2 244-261. (I haven't dug through the whole article.)

(I'm using "female" and "male" to mean people with at least two and only one X chromosome(s), respectively. I realize this is at best imprecise.)

The basic idea is that the genes for the pigments of the medium and long wavelength cones are on the X chromosome, and there's a surprising amount of polymorphism in them. When men get a "green" and a "red" gene which are too similar, they present with red-green color blindness. The mechanism proposed for female tetrachromatism is that, when one has two X chromosomes, one can have not just medium and long wavelength cones, but a medium-long wavelength cone type *in addition*. If having M and L is "normal", then having ML and L limits color perception, but having M, ML, and L can actually enhance it.

What Jameson et al did was actually genotype a bunch of subjects (typical psych-study volunteers) and found that women who had two alleles for at least one photopigment gene, and so had at least four photopigment types, performed significantly better at color discrimination tasks than women and men who had only 3 expected photopigment types.

This seems to be a non-stupid discussion of Jameson et al.

There's another article, Rodriguez-Carmona et al. 2008, Sex-related differences in chromatic sensitivity, Visual Neuroscience 25:3 433-440. It finds that women have significantly better color discrimination than men on the red-green axis but not the blue-yellow axis, which suggests again the mechanism of polymorphism in the X-linked genes for the green and red cones.

In any case, however, the added color discrimination is nothing like the degree of color discrimination in birds -- the added photopigments are within the normal human range, and, if anything, extend it only a little bit.

I am almost certainly making mistakes, confusing details, and interpolating wrong assumptions above; I'm an interested bystander in color vision theory, and the female tetrachromatism isn't even material we've presented to the students.

[signsoflife.livejournal.com]

(by the way, I'd really like to know how much sense that made, and what was especially unclear.)

[cos]

I say it's not a colour. It's a color. :)