These posts make more sense when read in order.
Please click here for the first article in this series to enter the rabbit hole.
I mentioned some illusions earlier, but not everyone experiences them to the same degree, and some don’t experience them at all. Part of this is based on culture and experience—how and where you were raised. Also, the ability to see some illusions diminishes as you get older. In addition, there also seems to be a link between the size of a person’s visual cortex and whether they can see some illusions or not. This area can vary as much as three times in size among individuals. Those with the larger area were less likely to see the illusions.[1] They have a more accurate view of the world, yet lose whatever advantage the ability to see illusions might provide. As there are still people who are one or the other, perhaps evolution is transitioning us from one to the other, or there is variability so that when our environment changes, one or the other will be better prepared. Interestingly, research shows that cats, rats, birds, fish, and insects do see the optical illusions they were tested on.
 |
| This photograph astonished people and sparked many debates because they couldn’t agree on its colors. |
In 2015 a Scottish woman uploaded an image of a dress that went viral on the Internet when people couldn’t agree on its colors. Most people saw it as white and gold, others as blue and black, some as blue and brown, then there were those who saw it switch back and forth. This seems to result from our brain’s varying assumptions on the type of lighting in the photograph. Yellowish light—whether from sunlight, incandescent, halogen, or household LED bulbs—causes your brain to subtract gold so you see a blue and black dress, whereas bluish light—from blue sky, florescent, or daylight LED bulbs—causes your brain to subtract blue, so you see a white and gold dress. Since the lighting conditions in the photograph are unclear, your visual processing system makes assumptions. Still, people were amazed that their friends, relatives, and colleagues saw it as a completely different dress. The dress is actually dark blue and black.
We think of colors as a property of the objects we are looking at, but that’s wrong. Objects absorb certain electromagnetic wavelengths and reflect others. How we perceive those wavelengths is all in our brain and varies from person to person, and from one species to another. Colors are not part of the physical world, they are something we experience in our minds. This has been known for a long time. Back in 1757, Scottish philosopher David Hume noted that “colour is allowed [i.e. acknowledged] to be merely a phantasm of the senses.”[2]
So, what about our basic perceptions?
There is a large variation there. The numbers of cones we have in our retinas varies by a factor up to 40. That’s a huge range. Overall females are able to see colors better than males. Still, there are some males at the top of the males’ scale that distinguish colors better than females who are near the bottom of the females’ scale. As with most everything, you’ll run into problems if you apply generalities to individuals, as that can lead to unfounded prejudices. There are color blind females, although they’re much rarer than color blind males. But in general the overall trend is there.
This is because females tend to have more cones than males. While they gain in color perception and discrimination, males tend to have more rods, so they have sharper vision, are better at detecting motion, and can see better at night. In addition, males’ cones have shifted so for males and females to see the same hue, males need a color with a slightly longer wavelength.
There is a similar variation in what a particular type of cone is sensitive to among individuals. Most often this happens with what we call the red cones—although they actually peak at yellow—but it happens with green as well. This is different from the seven types of color blindness and the differences are much more subtle than that—these are variations among people with normal vision.
There are many things that can alter our vision—genes, pathologies, past experiences, what we eat, the season, even our moods. Since colors are largely created in our brain, our perceptions of them can vary considerably and it’s difficult to tell what a person is actually experiencing when they look at a color. Scientists used to think we all saw colors the same way, but recent research has now convinced many that there’s considerable variation. “I think we can say for certain that people don’t see the same colors.” So said vision scientist Joseph Carroll of the Medical College of Wisconsin.[3]
So Alice could go through life seeing the world as slightly redder or slightly greener than the average person. Or what she sees as red could be what the average person sees as blue. She’d still call it red, since that’s what she learned to call it and nothing would ever indicate to her that she’s seeing anything different.
Something very interesting happens in the case of a few rare females. When one of the genes for red or green cones mutates to respond to another color, a female with that gene might end up having four types of cones. This only happens in females because they have two X chromosomes, which is where the genes lie. Males—not counting transgender individuals and those with Klinefelter Syndrome—have one X chromosome, so they have one gene for red cones, but these rare females have two different genes for red—one on each X. (That is, I think all the cases I know of all have an extra red gene and not green.) More than 50% of females have this anomaly, but with no effect on their vision because the extra color sensitivity is too similar to their other red cones, but there are a rare few who have four-color vision.
Now, a person with only rods sees in shades of gray. If they have one cone, they can distinguish around a thousand gradations of color. With two cones, they can discern about ten thousand colors. Most people have three cones and can see from one to two million different colors. Add a fourth cone that is significantly different from the others and the number jumps to a hundred million.
I’ve only seen reports of three women with tetrachromatic vision. One is a doctor near Newcastle, England known as cDa29 so she can remain anonymous, another is Susan Hogan in Pittsburgh, Pennsylvania, and the third is Concetta Antico in Byron Bay, Australia.[4] For them, each hue that we see is peppered with many subtler shades. Not just that, each object is a kaleidoscope of colors. What looks to us like a gray rock, to them is shimmering with colors.
Now, those of us with three working cones can see a lot of hues. One company, Borg Warner Chemicals, manufactured more than 2,000 shades of white, including pearl, frost, eggshell, and wisp. We can distinguish these. I can’t imagine how many additional shades these women can see. In addition, they have increased luminance, making colors brighter and enabling them to see colors at night.
Concetta Antico is an artist who incorporates this into her paintings, giving us a better idea of what it might be like to see the way she does.[5] For her, a simple green bush would be flecked with pink, lilac, orange, yellow, turquoise, and many other colors.
“I always felt like I was living in a very magical world”, she explained. “I know children say that, but for me, it was like everything was hyper-wonderful, hyper-different. I was always exploring into nature, delving and trying to see the intricacies, because I’d see so much more detail in everything.[...] I often think to myself, how could you be unhappy in this world? Just go sit in a park. Just go look at a bush or a tree. You can’t not appreciate how magnificent it is.”[6]
While what she sees must be stunning, there is a downside. She sees blemishes on her skin that are invisible to everyone else, and she says, “The grocery store is a nightmare. It’s like a trash pile of color coming in at every angle.”[7]
Compared to these women, those of us with “normal” vision are color blind. On the other hand, their amazing ability probably doesn’t rival the vision of birds who have between four and seven cones, depending on the species. Chickens have five. But, with their enhanced color vision, day-active birds need between five and 20 times as much light to see, so they can’t see well in twilight and usually head to their roosting spot soon after sunset.[8]
Theoretically it’s possible for a person to have five cones if they have working duplicates of both red and green cones that have deviated enough to respond to other colors.
There’s one caveat. The number of cones doesn’t necessarily mean better color vision. It’s possible some animals have more cones so they can see colors without needing complicated neural processing. The information from our three cones is heavily processed by our brain to create the colors we see. An insect’s brain is too small to do that. They might see only the colors their cones are sensitive to. A butterfly has 15 and a dragonfly has 30, so perhaps they only see 15 and 30 colors respectively. The mantis shrimp—a crustacean that resembles a lobster and is neither a mantis nor a shrimp—has the most complicated eyes in the world. Even though they have up to 12 cones, their discrimination between colors isn’t very good.[9]
Scientists at the University of Wisconsin–Madison believe they’ve developed glasses that can give those of us with three functional cones, four-cone vision. Perhaps someday they’ll reach the market.[10] There are already glasses available that give the color blind full-color vision.[11] Others are working on contacts. Researchers have also genetically engineered a mouse and two squirrel monkeys to have tricolor vision, so gene therapy may soon be an option.[12]
Since we tend to assume everyone experiences the world like us, many people don’t even realize they’re color blind, or have any other sensory deficiencies or enhancements unless something unusual happens to tip them off that something’s different.
Many people don’t realize they perceive the world differently from others until they’re in their 20s or older. Individuals fall somewhere in perceptual spectrums—such as from tone deafness to perfect pitch, and from face-blindness to super-recognizers—and most people have no idea where they are in those ranges. Sometimes even those at the extremes haven’t a clue until they notice something unusual or someone else points it out to them.
It’s obvious we have different preferences in food, clothes, books, music, and movies, but we don’t usually consider whether this is because of basic differences in our senses and how we perceive things.
Scientists have found we have fundamental variations in our perceptions. We even see the size and locations of objects differently.[13] Thinner people tend to hear sounds as being closer than they actually are, while women respond to looming sounds faster than men.[14] It seems we don’t even perceive sound patterns in the same way.[15] And each of us appears to have different olfactory blind spots.[16]
We learn about what music is when we are young. This is why newer types of music and exotic music from other cultures may not sound like music to us. People who grew up listening to big band music thought rock and roll was just noise, while many rockers felt rap was severely lacking, and rappers will no doubt feel the same about some new form of music. And all of them will probably have a similar view of traditional Chinese music, which sounds like caterwauling to many Westerners, although I believe you can learn to appreciate it if you are exposed to it in the right way. We can learn to like something new.
Just as everyone’s fingerprints are different, there’s evidence that everyone’s experience of the world is different, being altered by the differences in our senses and colored by our experiences. This is especially true when you compare two people from different cultures.
As noted earlier, our senses change throughout the day and throughout our lifetimes. Robin Carhart-Harris, a psychologist and neuroscientist at the Imperial College, London, pointed out, “Our brains become more constrained and compartmentalized as we develop from infancy into adulthood, and we may become more focused and rigid in our thinking as we mature. In many ways, the brain in the LSD state resembles the state our brains were in when we were infants: free and unconstrained.”[17]
Click here for the next article in this series:
[1] Wellcome Trust, "Brain's architecture makes our view of the world unique", ScienceDaily, December 6, 2010, http://www.sciencedaily.com/releases/2010/12/101205202512.htm, citing D Samuel Schwarzkopf, Chen Song, and Geraint Rees. “The surface area of human V1 predicts the subjective experience of object size.”, Nature Neuroscience, 2010, https://doi.org/10.1038/nn.2706.
[2] David Hume, “Of the Standard of Taste”, 1757, in David Hume, Essays, Moral, Political, and Literary Part 1, 1777, https://davidhume.org/texts/empl1/st.
[3] Natalie Wolchover, “Your Color Red Really Could Be My Blue”, Live Science, June 29, 2012, https://www.livescience.com/21275-color-red-blue-scientists.html.
[4] Mark Roth, “Some women may see 100 million colors, thanks to their genes”, Pittsburgh Post-Gazette, September 13, 2006, http://www.post-gazette.com/pg/06256/721190-114.stm.
And Bronwyn Adcock, “ ‘I’m really just high on life and beauty’: the woman who can see 100 million colours”, The Guardian, January 29, 2022, https://www.theguardian.com/society/2022/jan/30/im-really-just-high-on-life-and-beauty-the-woman-who-can-see-100-million-colours.
[5] Concetta Antico, https://concettaantico.com/.
[6] Bronwyn Adcock, “ ‘I’m really just high on life and beauty’: the woman who can see 100 million colours”, The Guardian, January 29, 2022, https://www.theguardian.com/society/2022/jan/30/im-really-just-high-on-life-and-beauty-the-woman-who-can-see-100-million-colours.
[7] David Robson, “The women with superhuman vision”, BBC Future, September 5, 2014, https://www.bbc.com/future/article/20140905-the-women-with-super-human-vision.
[8] The Swedish Research Council, "Birds lose color vision in twilight", ScienceDaily, November 16, 2009, http://www.sciencedaily.com/releases/2009/11/091111121543.htm, (comp.) citing Journal of Experimental Biology, 2009, 212, pp. 3693-3699.
[9] Stephen L. Macknik, “Parallels Between Mantis Shrimp and Human Color Vision”, Scientific American, March 20, 2014, https://blogs.scientificamerican.com/illusion-chasers/parallels-between-shrimp-and-human-color-vision/.
And Veronique Greenwood, “Eye of the Beholder”, New Scientist, no. 3017, April 18, 2015, pp. 40-43, and as “Eye of the beholder: How colour vision made us human”, April 16, 2015, https://www.newscientist.com/article/mg22630170-400-eye-of-the-beholder-how-colour-vision-made-us-human/.
And Jessica Morrison,” Mantis shrimp's super colour vision debunked”, Nature, January 23, 2014, https://www.nature.com/articles/nature.2014.14578, https://doi.org/10.1038/nature.2014.14578.
[10] Chris Baraniuk, “Glasses give us new power to see colours”, New Scientist, no. 3118, March 25, 2017, p. 10, and the longer version “Special glasses give people superhuman colour vision”, March 21, 2017, https://www.newscientist.com/article/2125335-special-glasses-give-people-superhuman-colour-vision/, citing arxiv.org/abs/1703.04392.
[11] Frank Swain, “True colours”, New Scientist, no. 3169, March 17, 2018, pp. 39-41, and as “New shades: The controversial quest to ‘fix’ colour blindness”, https://www.newscientist.com/article/mg23731690-900-new-shades-the-controversial-quest-to-fix-colour-blindness/.
Also, University of California - Davis Health, "Special filters in glasses can help the color blind see colors better, study finds: Effect persists even when glasses are not worn", ScienceDaily, July 13, 2020. www.sciencedaily.com/releases/2020/07/200713165608.htm, citing John S. Werner, Brennan Marsh-Armstrong and Kenneth Knoblauch, “Adaptive Changes in Color Vision from Long-Term Filter Usage in Anomalous but Not Normal Trichromacy,” Current Biology, 2020, https://doi.org/10.1016/j.cub.2020.05.054.
[12] Nicholas Wade, “With Genetic Gift, 2 Monkeys Are Viewing a More Colorful World”, New York Times, September 22, 2009, p. D3 of the New York edition, https://www.nytimes.com/2009/09/22/science/22gene.html.
[13] University of California - Berkeley, "Vision scientists discover why people literally don't see eye to eye: Study finds visual localization and acuity varies from person to person", ScienceDaily, July 14, 2020. www.sciencedaily.com/releases/2020/07/200714144735.htm, citing Zixuan Wang, Yuki Murai, David Whitney, "Idiosyncratic perception: a link between acuity, perceived position and apparent size", Proceedings of the Royal Society B: Biological Sciences, 2020; 287 (1930): 20200825, https://doi.org/10.1098/rspb.2020.0825.
[14] American Institute of Physics, “Wimps Hear Dangerous Noises Differently”, ScienceDaily, April 27, 2009, http://www.sciencedaily.com/releases/2009/04/090426094051.htm.
[15] Shawn Carlson, “Dissecting the Brain with Sound”, Scientific American, December 1996, pp. 112-15.
[16] Laura Spinney, “You Smell Flowers, I Smell Stale Urine”, Scientific American, February 2011, https://www.scientificamerican.com/article/you-smell-flowers-i-smell/, January 20, 2011.
[17]
Imperial College London, “Brain on LSD revealed: First scans show how the drug
affects the brain”, ScienceDaily,
April 11, 2016, www.sciencedaily.com/releases/2016/04/160411153006.htm,
citing Robin L. Carhart-Harris, Suresh Muthukumaraswamy, Leor Roseman,
Mendel Kaelen, Wouter Droog, Kevin Murphy, Enzo Tagliazucchi, Eduardo E.
Schenberg, Timothy Nest, Csaba Orban, Robert Leech, Luke T. Williams, Tim M.
Williams, Mark Bolstridge, Ben Sessa, John McGonigle, Martin I. Sereno, David
Nichols, Peter J. Hellyer, Peter Hobden, John Evans, Krish D. Singh, Richard G.
Wise, H. Valerie Curran, Amanda Feilding, and David J. Nutt, “Neural correlates
of the LSD experience revealed by multimodal neuroimaging”, Proceedings of the National Academy of
Sciences (PNAS), April 2016, https://doi.org/10.1073/pnas.1518377113.
Posts
