Alex Philippidis Senior News Editor Genetic Engineering & Biotechnology News
A possible explanation for the disparities goes back centuries to when men generally served as hunter-gatherers and women as nurturers and child bearers.
Men and women see things differently, and not just when it comes to asking for directions.
Women can differentiate between colors more finely, while men show more sensitivity to fine detail and rapidly moving objects, say researchers.
Why the gender difference on vision? The reason, researchers say, rests in differences between the visual centers of each gender. Men have 25% higher levels than women of testosterone receptors in their visual cortexes, where images are processed. As a result, their visual systems are better able than those of women to perceive changes in brightness across space, such as recognizing faces or reading letters from an eye chart.
Women, however, are better than men in distinguishing colors in the middle of the visual spectrum, such as shades of blue and green.
That’s because color vision depends on three types of cones, two of which are carried on the X-chromosome—L-cones that are more sensitive to the longer wavelengths of light; and S-cones, to shorter wavelengths. The third cones, M-cones, are sensitive to middle wavelengths.
“Across most of the visible spectrum, males require a slightly longer wavelength than do females in order to experience the same hue,” researchers from two City University of New York schools concluded in their study, published September 4 in Biology of Sex Differences.
For Women, Grass is Greener
Speaking with GEN earlier this month, the study’s corresponding author Israel Abramov, Ph.D., professor of psychology at Brooklyn and Hunter Colleges, said he could not venture what relationship, if any, the vision differences between the sexes might have with differences in the interests between men and women, such as in more contact sports or precision work by men, and in more aesthetic or creative disciplines by women.
“We cannot say how our results might underlie such differences,” said Dr. Abramov, who is also professor of cognition, brain and behavior, and professor of biopsychology and behavioral neuroscience, both at the CUNY Graduate Center.
“All we argue is that any higher functions must be limited by the information provided by the earlier, basic information—we are measuring events at the very early stages of processing by visual components in the brain’s cortex. These responses can be thought of as filters through which information about any image must pass,” Dr. Abramov added.
The study’s findings explain why women are likelier to see grass greener than do men, since green vision in males includes more of the longer-wavelength yellow. Or why when men see an orange, it takes in more of a hint of the color with the next longest wavelength, red.
It may not be an accident, then, that most men’s fashion items revolve around short-wavelength dark blue and three shades without wavelengths, black, white, and gray. Mens’ fashion blogs play up the color gender gap: “One of the things guys ask me all the time is how to match one’s clothes. This question pertains mostly to colors because that’s where us men have the biggest problems,” George Lazar wrote in a 2010 post on BeStylish!
Behind the gap is something more serious. According to the Howard Hughes Medical Institute, 7% of men are color blind, compared with 0.4% of women.
To assess perceptions of color among the sexes, the team of investigators from Brooklyn and Hunter Colleges assembled a group of 36 women and 16 men aged 16–38, with 20/20 vision—either naturally or through glasses or contact lenses—from undergraduates, graduate students, and faculty members at Brooklyn College, together with some high school students.
Participants were asked to describe colors shown to them. To measure their contrast-sensitivity functions of vision, the participants were also asked whether light and dark bars they saw were horizontal or vertical. Images appeared to flicker when light and dark bars alternated.
“It seems reasonable to conclude that male-female differences in basic sensory capacities are adaptive. Otherwise, why is this pattern found across sensory modalities?” the researchers wrote.
While males hold a sensitivity edge in vision, women enjoy greater sensitivity than men not only in hearing, but in smell, taste, and touch.
Another possible explanation for the vision and fast-motion disparities goes back centuries, to the evolutionary history of the sexes, when men generally served as hunter-gatherers, and women as nurturers and child bearers.
“Males, being generally larger and more powerful, would have to detect possible predators or prey from afar and also identify and categorize these objects more easily,” the researchers wrote. “It is noteworthy that sensitivities to low spatial frequencies is enhanced by temporal modulation; in the real world, retinal images are rarely stationary—objects move and the observer moves.”
Wesley Sutton, Ph.D., a visiting assistant professor at CUNY’s Queens College who was not involved in the study, told GEN that traits in a given species can usually be adaptations to its environment and lifestyle through its evolutionary history.
“Within the same species, differences between the sexes can often be understood by their different biological roles,” Dr. Sutton said. “In this case, assuming the differences hold in societies with different lifestyles (non-Westerners, farmers, hunter-gatherers like our presumed ancestors, et al.), it may simply be a side effect of the fact that during neuronal development males produce more androgens than females. In other words, there is no adaptive explanation.”
“The other possibility is that there is an adaptive advantage to males’ greater sensitivity to detail and movement, and/or females’ greater color sensitivity,” he added.
Dr. Sutton agrees with Dr. Abramov that with the adaptive advantage of the visual traits unknown, researchers will need to look for, then test, possible explanations: “It would also help our understanding if we could test for this difference in other primates, especially our closest relatives, chimpanzees and bonobos.”
That’s one avenue for further research into gender differences in vision. Another would be to repeat the vision and spatial relationships tests on a group more in keeping with the overall demographic mix of the U.S. than Brooklyn College—the demographic mix replicated by Dr. Abramov and his colleagues in their study—to see what if any factor race and ethnicity play in the differences seen between the sexes.
Within the college’s student body, women outnumbered men 61%–39% during the spring 2012 semester, compared with a slightly closer 57%–43% at all degree-conferring schools nationwide according to the National Center for Education Statistics. Even more disproportionate, whites comprised 30.99% of the Brooklyn student body, about half the national percentage of 60.5%.