Tetrachromacy means that you have four types of cone cells in the retina. Tetrachromats exist among birds, fish, amphibians, reptiles and insects, but in most mammals there are two kinds of cones, and in humans and some of our primate relatives, there are three kinds.
As you remember from high school, there are two types of photoreceptor cells in your retina. (Actually, they now say there are three, but the photosensitive ganglion cells aren’t there for vision). The rods work in low light; the cones work in normal light. The three kinds of cones respond, more or less, to short, medium, and long wavelengths.
In humans, those three cone types give us the capacity to distinguish a million color variations. Some men suffer from having two kinds of normal cones and a third, mutant, cone that is less sensitive to green and red. We call that color blindness. It’s a sex-specific trait.
In 1948 a scientist named H.L .de Vries studied the daughters of color-blind men to see if they might be carrying the mutant cone type along with their three normal ones. He did notice that the daughters of one of his test subjects responded to reds and greens differently than most women. Since then, a lot of people have searched for the so-called ‘four-coned woman’.
Turns out a significant portion of woman have dud ‘fourth cones.’ In June 2012, after 20 years of studying them, neuroscientist Dr. Gabriele Jordan identified a woman who could detect a greater variety of colors than trichromats could, meaning that she is a ‘true tetrachromat.’
One woman thus far. Yes, there probably are several more, but I doubt that includes you. For one thing, you’d need color-blindness to run in your family.
Visual information has to be collected and processed with retinal neurons and the resulting information sent via the optic nerve to the brain. It is processed and refined all along the way. What would the existing neural structure of the brain do with the information it got from a fourth set of cones if the infrastructure to interpret it wasn’t in place?
Human vision has plasticity that we don’t even begin to explore. When I first see painting students, they are puzzled about the color temperatures of white and grey. A year later, they’re manipulating color temperature like old pros. That isn’t because they sprouted new hardware; it’s because they’ve started to use the hardware with which they were born.
Want to see more color? Take up painting.
Registration is now open for workshops in 2026! Reserve your spot:
- Advanced Plein Air Painting | Rockport, ME, July 13-17, 2026
- Sea & Sky | Acadia National Park, ME, August 2–7, 2026
- Find your Authentic Voice in Plein Air | Berkshires, MA, August 10-14, 2026
- New! Color Clinic 2026 | Rockport, ME, October 3-4, 2026
- New! Composition Week 2026 | Rockport, ME, October 5-9, 2026
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If someone has tetrachromacy, it’s usually found in early childhood. My 1st grade teacher spoke to my parents regarding my struggle to decipher colors and recommended I see a specialist. After an optometrist referred me to 2 specialists, I was diagnosed with this condition; I’m reminded of it in every aspect of my life regarding everyday things. Yes, it’s rare, but not impossible, so I find it odd that someone not in the field of optometry or genetics is making statements telling strangers they don’t have tetrachromacy while comparing it to learning and practicing painting skills. Also, this blog makes it sound like color blindness running in a family is rare, when in reality 1 in 12 men have the condition. I also think it’s important to note that someone’s economic status and access to doctors/specialists plays a big role in being properly diagnosed, and I’m sure there’s more of us out there.
Tetrachromacy requires that there be four independent photoreceptor cell classes with different spectral sensitivity. To date, only one woman has ever been identified as having a fourth-cell class mutation.
There must also be the appropriate post-receptor mechanism to compare the signals from the four classes of receptors. Our best understanding is that humans have three opponent channels, which give trichromacy. The likelihood of a combination of a fourth photoreceptor cell class and a fourth post-receptor mechanism is infinitesimal. Until research shows such combination exists, I will continue to disbelieve in it.
The projection of tetrachromacy has been from behavioral studies, and there is much deviation in individuals’ ability to discern color. I notice this in the blue range when teaching plein air. That in part can be explained, I think, by learning to differentiate color, as artists must do.