Why do our eyes see in color? Neuroscientist Mark Changizi examines this question in his book The Vision Revolution. He says that the human eye evolved to see colors in part to glean what another person feels by detecting subtle color changes in their skin. He told EarthSky:
One of the most important things in our lives is other people’s faces, and the skin on those faces. The brain really cares about seeing the small differences.
He said color changes that happen on our faces – like blushing – reveal a lot about people.
You can discern a lot about what’s going on in their brains, what their mood is, what their state is, what their current emotion is.
Changizi added that being able to see colors can also clue people in to the health of others.
In the medical communities, they’ve long used color within the symptomology within certain diseases. And if you’ve ever had a kid, they’re color-changing all the time. When they clench to fill their diaper, they’re immediately purple. Their face is brilliantly purple. Every little thing that they do, their faces are changing much more quickly. Much of this is medical related, and much of this is emotion related. But more generally, the idea is that it gets you a view into the underlying state of another human.
Photo Credit: helgabj
Changizi said the human eye has a particular part that enables us to see these subtle color changes. Dogs, for instance, can only see blue, yellow, black and white. They lack the receptor, or cone cell, for seeing red and green. He said:
As I looked into it, I was able to work out, on the basis of oxygenation of hemoglobin that underlies these changes in your skin, what would our cones have to be like to be able to sense the oxygenation and de-oxygenation of hemoglobin.
It turns out you have to have a really peculiar type of color vision, one where you have a new cone that’s almost just like one of these mammalian cones, it’s almost in the same spot, but a little shifted over. You have to have cones like that in a peculiar way, in order to sense the spectral changes that happen on the skin, or to see the emotions of others, you have to have the funny kind of color vision that we have.
Listen to the 8-minute interview with Mark Changizi on why our human eyes see color (at top of page).
This is really interesting – I never knew that dogs are able to see in blue and yellow. I always heard they only see in black and white.
I have a theory about human male red-green color blindness. Hunters and warriors would be much less distracted and grossed out if they couldn’t tell blood from grass so easily. Female gatherers, on the other hand, need to differentiate ripe fruit and new shoots from foliage.
Try again with the theory. Color vision evolved in primates sometime in the last 40 million years, long before the first human cried “ma ma”. Primates (humans excepted) are hairy, and very dark-skinned. It is hard to spot blushing (all humans do it) in people and other primates with darker skin, especially if their faces are obscured with hair! Chimpanzees have skin that is nearly coal black, and do not show any sign of blushing, if they do it at all. (nobody really knows.) Caucasians, whom it is easy to spot blushing, evolved in the last 20,000 years or so – long after color vision. Asians evolved lighter skin at about the same time. Neandertals evolved light skin separately, unfortunately there is no data on their blushing habits. Before the Neandertal, all humans had universally dark skin and blushing would be subtle at best. This looks suspiciously like a caucasian-centered theory to me.
There are some primates who have reddish buttocks during estrus, (not many) but it is more likely colorful food sources that drove evolution of color vision in primates, which is the more conventional view.
I like the way this sounds. And I don’t know when these species became this way, but there are colorful frogs that indicate to humans and other species of animals that they are poisonous. Some animals instinctively know that they are poisonous. Basic evolution and survival required that we see in color. We evolved and adapted.
Good thoughts, Lawrence…Advantages in telling food from non-food, and possibly differentiating between spoiled food and food that was safe, or picking out game animals or edible insects against a predominantly brown or gray or green landscape seem more reasonable evolutionary drivers than looking for blushing…
Some people reason, some try to think with their emotions.
Oh, and if you’re dependent on hunting for survival, the sight of red is a positive reinforcement, not a gross-out…it means you’re likely to have something to eat rather than to be eaten by something or to starve.
I’m a red-green colorblind male, myself. I was told when I was in the military that it gave an advantage in seeing through camouflage…colors that were blended and balanced to appear the same to normal vision stand out to a red-green color blind person…no proof, just a theory.
Dr. Changizi explains in The Vision Revolution that humans and some primates share having ‘bare spots’ along with furry skin. “Indeed,” he writes, “the primates with color vision are the ones with the bare spots on their faces, while the primates without color vision have typically mammalian furry faces.”
Check back tonight and I’ll post a link with a scan from a color plate in the book showing representative primates.
Thank you for your comments! I’ll see if I can get Dr. Changizi to reply as well.
I am color blind(what is called a red/green deficiency). Is there any hope for a color blind person to gain correct or improved color perception. I would be a willing “guinea pig” for any solution.
What does this say about women wearing makeup