A continuation of our "greatest hits" from past Cognitive Daily postings:
[originally posted on September 27, 2005]
All this talk about stereotypes can get you thinking. Perhaps some stereotypes reflect actual differences. Take color vision, for example: men often refer to themselves as "color-impaired," letting the women in their lives make home design decisions and even asking them to match clothing for them. Maybe they're just behaving in accordance with traditional stereotypes ... but maybe there's something more to it.
In the 1980s, vision researchers began to find some real physical differences between the eyes of many women and those of most men. "Normal" color vision is possible because we have three different types of cone cells in our eyes, each of which responds to a different wavelength of light. The process is basically the reverse of how a TV set or computer monitor works: on a TV, there are three different colored dots—red, green, and blue—and the millions of "colors" we see are based on mixtures of different proportions of those colors. In the eye, cone cells can have three different photopigments. These are usually generalized as red, green, and blue, but their actual values are closer to yellowish green, green, and bluish violet. To avoid confusion, psychologists typically refer to them to long-, medium, and short-wavelength sensitive cones. Supposing we're looking at a yellowish-green thing, the long-wavelength cones are stimulated the most, the medium-wavelength cones are stimulated a bit, and the short-wavelength cones are not stimulated at all, and the appropriate signal is sent along the optic nerve to the brain, which then recognizes the color as "yellowish-green."
What the researchers were finding when they actually looked at the structure of the eye is that many women—perhaps over fifty percent—possessed a fourth photopigment. Was this merely a genetic anomaly? Would the brain even be able to process this fourth input? The early research suggested that it would not. Women were no better at determining whether two very similar color patches were actually the same. They were only slightly better than men at detecting subtle spots of red light, a fact researchers attributed to individual difference.
However, Kimberly Jameson, Susan Highnote, and Linda Wasserman were not convinced by this evidence. Five- and six-year-old girls are better at naming colors than boys, and grown men are not as good at color-naming compared to women. They felt the existing measures of color sensitivity and color-matching did not capture all the differences between men and women, and devised a new experiment that they felt was more representative of real-world vision.
It's quite difficult to examine an eye to determine if it has the fourth photopigment—the process generally involves removing the eye itself. Jameson and her colleagues might have had just a bit of difficulty recruiting volunteers to participate in an experiment requiring such extreme measures, so instead they used a genetic test to determine how many different photopigments participants were likely to possess (they estimate this process to be about 90 percent accurate—biologists will recognize this as the genotype versus phenotype problem). Of 64 participants in the study, 23 were women with 4 photopigments, 15 were women with 3 photopigments, 22 were men with 3 photopigments, and 4 were men with 2 photopigments (this is commonly called "color-blindness," but most people with 2 photopigments can still distinguish between many colors).
Next, participants viewed a spectrum projected on a lucite window covered with tracing paper. Over the next hour and a half, they performed an array of tasks, including marking the edges of the visible rainbow, marking the locations of the "best example" of each of the major colors, and marking the edges of each "band" of color in the rainbow. Between each task, a camera flash was set off to mask the previous spectrum example, and the experimenter mounted a new sheet of tracing paper on the panel.
The most compelling results came from the number of spectral bands task:
|Type of participant||
Average number of spectral bands
Number of participants
|Three-pigment males and females||
Four-pigment females perceived significantly more bands of color than both three-pigment males and females. Further, three-pigment males and females are statistically indistinguishable, suggesting that the result is not due to some cultural difference between men and women.
So why were others unable to find significant results in a color-matching task when we see such dramatic results here? Jameson et al. suggest that there may be two (or more) different modes of seeing color, each processed differently in the brain. The brain may use the data from all four photopigments for some processes, but not for others. But this is still supposition. What's clear from this study is that the stereotype of women being better with color may reflect real differences between men and women.
Jameson, K. A., Highnote, S. M., & Wasserman, L. M. (2001). Richer color experience in observers with multiple opsin genes. Psychonomic bulletin and review, 8, 244-261.
Women characteristically see the red end of the spectrum better than men do. Has no one wondered why it is Mom who can look at the kids and see one is overheated (a little too red) and the other is getting sick (looking a little green), while Dad doesn't see any difference?
I grew up in northern Appalachia, where the leaves changing colors in the fall is quite a spectacle. However, to me the colors looked ugly, except if it was raining or snowing, when they looked nice. Being male, the bright blue sky overwhelms my color vision so that I detect red poorly. In foul weather, the lighting itself is whitish, so the colors are not bleached by the blue.
Now I live in California. I noticed on one long street with many traffic lights that I could see green lights clearly a mile ahead in bright daylight but couldn't make out the red lights until I got much closer. When I got new sunglasses, I ordered neutral gray, but the supplier made a mistake and made the lenses rose colored. With these, I can see red lights as well as I can green lights miles away. I also see autumn leaves as having nice colors instead of ugly colors.
I'm not surprised by the 4th type of cones.
Incidentally, I tried a spectral test like that on a woman who is color blind. She found that the results explained a lot about her problems. (She shops with female friends and has females pick out her outfits. Smart solutions.)
Drat just proved what I've always suspected---that women wear rose-colored glasses. Must be a survival tactic to keep going through impossible odds in order to get those children raised and into a positive way of life. (just kidding!) :-)
Actually, I think color perception is more of a matter of "paying attention" than anything else. One can train oneself to "see" color, and I think women usually just pay more attention to life in general and are more sensitive to their surroundings in different ways from men. Maybe that's because men have had to train themselves to be in the "warrior mode" through the eons, where instant survival is more important than color sensitivity.
A person trained in the arts will also have better color perception, either male or female, because they have to pay attention when they paint. I have a male friend who is not in the least artistic, even when you explain to him that the reddish-brown earth in the hills combined with the blue in the distant atmosphere obviously makes "PURPLE". He cannot see the "purple" in the hills, whereas other male friends who are artsy can see purple as well as any woman can. To the male friend who cannot see the purple the hills are "brown" and that's that. He doesn't even want to discuss any other option or any nuances. His paintings would all be different shades of brown, I think, just because he refuses to acknowledge anything but the obvious brown.
So, even though the eye and brain have their "perceptions", if the eye and brain are within the normal range, one can train oneself to see color nuances.
roseindigo, I don't think that is the whole story. Obviously training is going to have something to do with it, but why shouldn't there be both genetic and physiological differences in what can be perceived? There are genetic and physiological differences in the ability to taste and smell which are not simply differences in training and experience (e.g. "supertasters" who have more taste buds per square centimeter on their tongues), and people have different levels of sensitivity to heat, cold, pressure and pain stimuli based on the physiology of certain nerve cell receptors, as well as training and expectation. Why not the same sort of variation for vision?
Personally, I know that I display some variation in sensitivity to color as a result of physiological differences. Oddly, my right eye perceives blues and greens more strongly, and my left eye perceives reds and oranges more strongly. I can pick out variations in those colors better in the respective eyes on color blindness tests. I assume that this is a result of different concentrations of cones in each eye, rather than some oddness of my brain, since it seems a more likely and parsimonious explanation.
Luna, I do agree with you that there may very well be a genetic component to vision, just as with the other senses. For instance, I have a VERY acute sense of smell that most people do not have. If I'm out in the wilds I can "smell" if humans have been anywhere in the vicinity recently, and I can "smell" the tiniest amounts of gas even when the gas company can't find it. And it may very well be that vision varies in the same way. But what I'm not sure of is that it varies between men and women in general, except insofar as women display more sensitivity to color by paying attention to it.
When one refuses to "see" in the way my friend described above refuses to see the purple, one doesn't see it, and that's that. I think as far as senses go men are much more apt to refuse to see or feel the nuances. It's just RED, and that's all they care about. Women seem to be able to tell the difference between a tomato red and a carmine red, and can NAME THEM; but that's because they are paying attention. And what I am saying is that one can train oneself to be more observant.
So, even with the genetic differences amongst individuals anyone can still train themselves to be more observant and notice the nuances in color, whatever their genetic disposition may be.
I'm not saying anymore than that.
I suspect you are a female simply because you have actually noticed the difference in your visual perception of color of one eye compared to the other. That's what I mean by PAYING ATTENTION.
You would have to control the subject's exposure to light hours in advance of the study. For example, if I were to leave one subject in a dimmed light environment (in which they slightly strain to perceive light) for even 10 minutes, I could guarantee they will perceive more bands of color in the test. If they are testing an eye's perception of light, then they need to go to every measure possible to control the subject's exposure to an equal amount of light leading up to the experiment. I would also like to know the control in the experiment.
roseindigo -- how do you know that your friend is willfully refusing to see any shade but brown even though he could? Have you considered the possibility that he defends the (to him) "fact" that there is nothing there but brown because he literally can't see anything but brown, and doesn't look for subtler shades of blue because he has never seen them?
You're correct that I'm female, but I would say that I pay attention to my eyes less because I'm female and more because I've had weird problems with my vision in the last couple of years (acute macular neuroretinopathy), which is enough to make anyone hypersensitive to what their vision is doing.
I'd also go so far as to say that women probably tend to become more sensitive to visual cues than men, where women are in less dominant and more sensitive positions. It's a survival thing to be able to pick up on tiny mood shifts, and the people who need to learn this, do, and the people who don't, tend not to, with obvious variation for things like borderline autism. You see a similar hypersensitivity to visual cues in abused children of both sexes.
I would be interested in seeing a version of this test done on both men and women (of all cone types) who had been classically trained in art and color theory. The spectrum test is an excellent way to tell, given that the ability to name colors might only reflect a subjects depth of vocabulary or linguistic ability, not whether he could see the color itself. Artists can often pick up on minute color differences that laypeople might miss. Just as men are able to find an imbedded object in their field of vision faster, (helping with hunting), it would be an evolutionary advantage for women to be able to distinguish some of these subtle nuances, as they were historically more involved with food gathering and child rearing. Most of the senses in women are physiologically more broad and more finely tuned- which has nothing to do with men choosing to be oblivious to the baby crying, or to the draperies matching (or even his own B.O.)- men are often oblivious because they really can't hear it, see it, or smell it. I think that any of the senses can reach a full potential of development with training, or with practice, but if the faculty is not there to start with, no amount of art class will teach a color blind man how to see the difference between carmine and scarlet.
Human women could have evolved down a similar path as birds, whose courtship displays involve diverse songs and beautiful plumage on the part of the male. Females would need the ability to perceive them, thus evolving the means to do so.
I'd seen some articles on tetrachromatic women, but the numbers given here seem surprisingly high, and the breakdown is dubious.
In any case, even basic color vision certainly varies widely among individuals -- my own family features enhanced color vision running from my maternal grandfather. We call it "artist's eyes" -- most of Grandpa's descendants (including me, the lone adult male) have taken a turn at some sort of visual arts. (Oddly, my Dad was partly colorblind.)
Luna, your interocular differences could have several sources, such as a developmental hiccup, genetic chimerism, or differential effects from your condition.
Yet another issue is the one roseindigo brings up in #4, but she seems a bit confused about it: Normal human vision goes through a heckuva lot of processing before it even gets to conscious attention. Most "neurotypicals" spend most of their attention dealing with their mental "summary" of the world around them, rather than direct perceptions. This layer of processing also deals with many "threshold" issues, filtering out weak stimuli in favor of the overall picture.
And then there are those folks for whom that filtering layer is damaged or nonfunctional.... In particular, peouple with autistic spectrum disorders are well known to suffer an assortment of problems with sensory sensitivity and thresholds -- but in recent years, it's become clear that those issues are part of more general disruptions of that "world-interpretation" layer. Note that it's also possible to "make lemonade" from these differences -- as Dr. Grandin demonstrates so clearly, the less-filtered view of the world does have some useful information -- which "NT's" tend to look past.
I'd like to comment about these two sentences from above:
"given that the ability to name colors might only reflect a subjects depth of vocabulary or linguistic ability"-----I believe this is very true. In our society, if we don't have a name for something, it is often not visible. The language we use is what helps us think and actually helps us to "see", and the larger our vocabulary the more nuances we will be able to see and describe. If I don't have a word for "carmine" and "scarlet", then the object I'm looking at is simply "red", and it takes some training to see beyond that generalized "red". If someone has normal vision, that can be done and their horizons can be expanded.
And regarding this: "Most "neurotypicals" spend most of their attention dealing with their mental "summary" of the world around them, rather than direct perceptions."
If I am understanding this sentence correctly, this is why most people claim they cannot draw or paint. It has less to do with talent than it has to do with people being in the habit of making mental summaries. Even for a trained artist those mental summaries get in the way. A table is a flat surface with four legs, and when asked to draw a table that is the way most people draw it, but they are not using direct perception which includes angles, ratios, perspective, etc.
Actually mental summaries are a great survival skill. When I'm out on the freeway I make quick mental summaries of my surroundings in order to avoid an accident. I don't have time for nuances. But I think people get into THE HABIT of that, and make mental summaries when other modes of perception may work better, depending on the circumstances. Quick mental summaries are fine when driving a car, but not very useful if I'm looking at flowers in a garden.
If I don't have a word for "carmine" and "scarlet", then the object I'm looking at is simply "red", and it takes some training to see beyond that generalized "red".
I have no idea what the differences between "carmine" and "scarlet" are, but I can still distinguish between shades that I would still call "red". The point of the tests was that the subjects did not have to name anything - just see a difference between one shade and another.
Their DNA test separated the subjects into groups with an expected 2, 3, or 4 photopigments, and those subjects with more pigments performed better, as expected.
Controlling for this effect, they saw no difference between the sexes, which suggest that any differeces between the sexes in life experiences, interests or tendency for "PAYING ATTENTION", had no effect.
It is just that the average woman had more photopigments than the average man.
It is not that unlikely - something similar occurs in New World monkeys.
There are some possible gene issues between females and males with regards to color blindness according to the site http://www.eyecaresource.com/conditions/color-blindness/
Well, this article lends validity to what I suspected all along: that my husband cannot properly name certain colors even though technically he is not colorblind. We argued alot about colors in the beginning stages of our relationship. He never believed me when I said that he was wrong about the name of a color. I'm not talking about naming the shades, I'm talking about naming the basic colors: red, orange, yellow, green, blue, purple, pink, white, brown and black. I think where he gets confused is when the colors are not "true." When he sees different shades of the basic colors, that's when it gets difficult for him to name them.
This is something I've only thought of within the last few years and I've personally assumed that some of it would be socialized and some of the differences would be down to something physiological without having any evideence for it. I began to think of it when I thought that it was odd that my three boys have very strong color preferences and not the expected blue or green favorite colors of most boys. The oldest prefers yellow and can name many different yellow shades. The middle one prefers pink, Barbie pink to be precise and out of 85 color pens and several of them being shades of pink, he picked out a medium pink that definitely looks Barbie pink the way I remember it as a girl in the 1980s. He also has many names for different pink shades. My youngest one prefers red. The brighter the better and other than that he notices blue and green a lot and he doesn't seem to discriminate that much between shades of red but that could be down to lack of vocabulary; He has automotoric retardation. When they play together and color choices come into play while fx. playing with Lego, the constructions will mainly be red, yellow and orange. They only have a few pink Lego blogs. The middle one wanted purple rain boots and not blue ones. Purple has a bit of red in it, right?
I wonder if my boys see differently than most males, if it's measurable and/or why they see differently than other males be it psychological or physiological.