Posts Tagged ‘bare skin’

Christine Ottery (that’s not her above) recently interviewed me about bare naked skin and the origins of color vision, and she wrote up her piece in Scientific American. Read it here.

Also, note the “Lady Gaga” connection in the piece. This is not the first time “Lady Gaga” has been all over my research — the words, not the actual woman. She also comes up in a story about my research on the origins of music, which you can read here at Gaga-galore.

Let’s keep up the pressure, and perhaps Lady Gaga will hire me as her scientific aesthetics advisor…


Mark Changizi is Director of Human Cognition at 2AI, and the author of The Vision Revolution (Benbella Books) and the upcoming book Harnessed: How Language and Music Mimicked Nature and Transformed Ape to Man (Benbella Books). He is working on his fourth book at the moment, tentatively titled Making Faces, about emotions and facial expressions.


Read Full Post »

EarthSky interviewed me in late 2010 about my book, The Vision Revolution, and the segment about the evolution of bare skin and color vision was the second most popular interview in that year. Hear the interview yourself here.


Mark Changizi is Director of Human Cognition at 2AI, and the author of The Vision Revolution (Benbella Books) and the upcoming book Harnessed: How Language and Music Mimicked Nature and Transformed Ape to Man (Benbella Books). He is working on his fourth book at the moment, tentatively titled Making Faces, about emotions and facial expressions.

Read Full Post »

The press release just came out for my simple proposal for harnessing our color vision for better sensing clinical skin color changes of patients, along with some news stories, which can be linked here…

LA Times, Toronto Sun, Forbes, Times Union (and video), Troy Record, BoingBoing, AOL News, Times Colony, Diagnostic Imaging, Ratschlag24, Press Release, and my own SB piece. Also, here’s the paper itself.

This proposal for medicine is a corollary of my research on the evolution of color vision — it’s for seeing emotions and states on the skin of those around us — something you can read about in my book, The Vision Revolution. I have a variety of pieces on the research here.

And here’s a figure that helps summarize the “oximetry” point in the press release…

Mark Changizi is a professor of cognitive science at Rensselaer Polytechnic Institute, and the author of The Vision Revolution (Benbella Books).

Read Full Post »

“But I thought you were blue!” That’s what Jake Sully, the main character in Avatar, says when he wakes up as an alien at the very end of the movie. Actually, the movie ends just before he has a chance to say anything, but that’s my guess about what he would have said. The question is: Why would he say that? (Or, if you’re a stickler: Why would I say he would say that?)

For those who haven’t seen the film, what you need to know is that Sully is a human who, from the safety of his brain-interface chamber back at the lab, can remotely control a “soul”-less alien body. And, at the end of the movie, and through the miracle of human suspension of disbelief, his human self gets literally uploaded into the alien’s body. Sully thereby becomes a bonafide eight foot tall, blue alien, and in the final frame of the movie we see his alien eyes open.

Question is: What does Sully see when he opens his eyes? And, more to the point: Does his new alien wife still appear blue to him?

By way of answering, let’s back up and remember what visual systems are for. When we look out at our world through our eyes, we implicitly believe we are seeing it as it truly is. Our eyes and visual systems are to us objective scientific measuring devices. But evolution does not select for objective scientific equipment – evolution selects for visual systems that best serve the animal and its reproduction. Although often the best perception is one that veridically reflects the truth, sometimes the best solution is a “useful fiction,” a little-white-lie perception that serves us better than an accurate accounting of the actual.

Consider the accent of your own voice. To you, you have no accent. It is other people that have an accent. And they think it is you that have an accent. Perceived accent, or “accentness”, is not a quality of the speech stream itself. Accentness is not an objective perception of anything out there. It depends on the baseline accent one has become adapted to, namely your own. When one adapts to a stimulus and it becomes baseline, the “qualitative feel” of that stimulus diminishes, i.e., it begins to feel like nothing to perceive it. The benefit of this is that even very  tiny deviations away from the baseline feel perceptually highly salient. Your own accent doesn’t sound accented because it is your baseline accent, allowing you to be trigger sensitive to the modulations around it from the voices of different people and their different emotional inflections. This is also why you don’t notice any smell to your own nose, any taste to your own tongue, or any temperature to your own skin.

And, in addition, it is why you don’t perceive your own skin to be colorey. People perceive the color of their own skin (or that of the most common one in their experience) as uncolorey and difficult to name. This perceptual adaptation to the baseline skin color allows people to be highly sensitive to the subtle color modulations happening on the skin of others as a function of mood or state.

Now we can circle back to our earlier question. When Sully opens his eyes as an alien, does his alien wife still appear blue to him? And the answer is no. He’s one of them now, and will perceive his wife’s skin, and his own skin, as peculiarly uncolorey, no longer blue at all. He will also not notice the taste of his own alien saliva, something you can be sure he would have noticed were he to have tasted alien saliva as a human. And now we see why alien Sully exlaimed, “But I thought you wereblue!” Let’s just hope he wasn’t into her only because she was blue!

Other pieces about color vision and skin are here, and also play prominently in my book, The Vision Revolution.

This first appeared on January 6, 2010, as a feature at the Telegraph.

Mark Changizi is a professor of cognitive science at Rensselaer Polytechnic Institute, and the author of The Vision Revolution (Benbella Books).

Read Full Post »

This first appeared on January 18, 2010, as a feature at ScientificBlogging.com.

If you ever have a mysterious skin rash and show your doctor, he or she may very well take a marker and encircle it, and then ask you to come back in a week. What’s the marker for? That’s obvious. If the rash is expanding, it may grow by only, say, 5% in a week, far too little to notice. But with the marker pen tightly encircling the original extent of the rash, any growth in the rash will become perceptually obvious because it will have grown beyond the boundary of the marker pen.

As obvious as this is for rashes, this basic principle is not currently followed for the much more acutely important skin color changes that occur in various medical conditions. Despite skin pallor having had a long history within medicine diagnosis, the medical community is currently handicapped in its ability to visually sense clinically relevant skin color modulations. For skin color, medicine is markerless. If a doctor sees a patient, and then sees the patient again later, the doctor will have little or no idea whether the skin has shifted. Quantitatively small color shifts can have tremendous medical implications: it can, for example, mean the difference between having healthy oxygen saturation and life-threateningly low oxygen saturation.

But we can do better. Our eyes have evolved, so I have argued in my research, to be near optimally sensitive to skin color changes due to underlying physiological changes in the blood. The skin color changes that mattered over evolution were socio-sexual signals, and socio-sexual signals tend to have strong spectral gradients our oximeter eyeballs are great at detecting. In fact, our eyes depend on these gradients to see skin colors. For example, our perception of blue-green veins depends crucially on its contrast with the surrounding skin. Blue-green veins if viewed all by themselves (i.e., through an aperture) do not appear blue-green at all. Veins are just slightly spectrally shifted toward blue-green compared to the skin’s baseline color, but when seen with the baseline color in the spatial surround, one sees the veins as genuinely blue-green.

Clinical color changes, on the other hand, are not selected to be seen – they are just side effects of being sick – and can often lead to much more spatially uniform shifts in color. And that’s the problem. If a patient’s skin color shifts a small amount for many clinical reasons (like central cyanosis), then when the doctor or nurse comes back, the color shift will often be imperceptible.

We can, however, fix this with a little marker pen. Rather than encircling the baseline extent of the rash, we need a marker pen to record the baseline color of the patient’s skin. And one place to begin marking up is the beloved hospital gown (although the same point will apply to any other colors visually proximal to the patient, such as the walls or sheets). The problem with hospital gowns is not just the drafty bum, but that gown colors are not designed to harness the oximetric, blood-diagnosing powers of our eyes.

The figure below shows four sample hospital gown colors, and on each of these colors I have placed the same five patches of skin. The central patch, let us presume, is your baseline skin color. The patches around the central patch are slightly color-shifted from the baseline, namely (from top, clockwise) bluer, redder, yellower and greener. Even with the baseline pitch there in the image, the color shifts are not perceptually salient. All the patches look qualitatively like the baseline patch’s color. And in real life the nurse or doctor would see the central patch, and then come back later and see just one of the shifted colors – determining if the color has changed would be nearly impossible.

mark changizi nude colored gown color changes

But now consider what happens if I lay those same five colored skin patches adjacent to a gown that has a color matching the baseline skin color in the center. In the figure below the four color-shifted patches look utterly and qualitatively distinct. They don’t look just a wee bit bluer, redder, yellower and greener than baseline. Rather, they now look distinctly blue, red, yellow and green. Again, these are the exact same four patches as were in each of the “gowns” in the previous figure.

mark changizi nude colored gown color changes

Here, then, is the simple prescriptive advice for hospitals: buy skin tone colored gowns, with colors relevant for the population you serve, and have patients wear a gown that best matches their baseline skin color. The tighter the color match, the more hypersensitive the eyes of the nurses and doctors are at sensing tiny spectral shifts away from baseline. I also suggest “skin color adhesive tabs” in a recent publication, which you can read here: http://www.changizi.com/colorclinical.pdf

Are these ideas relevant, you might ask, given that hospitals these days have cheap access to oximeters? Here is what co-author Kevin Rio and I write about this at the end of the article I just mentioned above:

One may wonder if these two techniques for harnessing color vision for oximetry are relevant in modern medicine, given the availability of pulse oximetry. [T]he clinical disciplines most utilizing pulse oximetry are also the disciplines that most often refer to the patient’s clinical skin color in diagnosis: thus, the actual practice of medicine appears to value our human color capabilities, despite the presence of pulse oximetry. There are several potential explanations for this: (a) color perception provides redundant detection of oxygen saturation (e.g., if the oximeter becomes unattached), (b) observation of skin color modulations may lead to a faster behavioral response by the clinician (the “look” of sickness may be more psychologically engaging than numbers or beeps from an oximeter), and (c) our color perception is capable of sensing the spatial gradients in skin color across the body, and the nature of those gradients can impart information to a clinician. Furthermore, there are circumstances where pulse oximetry is not used today, but where the “color oximetry” techniques above would be of great value: (i) in certain parts of the hospital (e.g., in transit, or the emergency department waiting room), (ii) in third world hospitals, where it is still not part of standard care, (iii) in the field (e.g., for athletes or soldiers, and (iv) in the home (e.g., for SIDS detection).

Haiti comes to mind.

Mark Changizi is a professor of cognitive science at Rensselaer Polytechnic Institute, and the author of The Vision Revolution (Benbella Books).

Read Full Post »

Today I was on LateNightLive (of ABC Radio National) with host Phillip Adam.  In addition to divulging my enjoyment at running over pigeons, I got a chance to talk about sex, blood, the blind, writing, rabbit-heads and other topics from The Vision Revolution.

Late Night Live

Late Night Live

Check out the segment here. (Download the mp3.)

Mark Changizi is a professor of cognitive science at Rensselaer Polytechnic Institute, and the author of The Vision Revolution (Benbella Books).

Read Full Post »

Originally a piece in ScientificBlogging, October 10, 2009…

I need most of my body parts. I figure I have my various meaty chunks for good evolutionary reasons, and far be it from me to sell any, no matter how often that creepy guy shows up at my door with a cooler of dry ice offering me money. But if I ever were going to unload one of my body parts, I’d pick the most useless one of all, one that is even more useless than the appendix (although even it has recently been suggested to not be so useless, “Your appendix and your eyes.”)


I would sell my belly button. To illustrate just how useless it is, can you recall when you last used it? I bet you can’t. It is well known that the more common “innie” variety accumulates lint from your clothes (mostly your underwear) over many months, which could be useful if you’re interested in knowing what the average underwear color of your date is – although if you’re close enough to get a good lint sample, my bet is that there is little mystery about the color of the underwear.

Is underwear color documentation the only use of the belly button? Could it have some better function? Has anyone done the perfect experiment where one removes the belly button? Maybe we’re dead in 15 minutes without a belly button! That does seem unlikely.

At any rate, anyone who knows anything will assure you that there is, of course, absolutely no function for the belly button. It is just the remnant scar from the umbilical cord, the cord which was useful while in the womb.

But I’m not so sure.  Mind you, unlike much of my research where I put forth and test an actual hypothesis for what some biological feature is good for (e.g., color vision, forward-facing eyes, the shapes of writing, illusions, number of limbs, brain anatomy), for the belly button I don’t have any hypothesis at all. For the navel I’m drawing mostly a blank. Nevertheless, there are several reasons which suggest that the belly button is not simply a developmental leftover.

First, do you have any idea how many strange things happen to our bodies during development?! Our wee bodies undergo massive transformations, with certain anatomical features appearing at one stage (e.g., tail-like appendages), and completely going away later. All this is crucial for building fancy machines like us. Just as buildings have scaffolding during construction, but don’t end up with scaffolding scars left on them, biology can build structures during development that are needed during development, and that completely go away later. All these developmental back-flips occur, and then get “covered over.” Why not the belly button?

Second, in most mammals the belly button does, in fact, get covered over. Have you ever rubbed the tummy of your dog or cat and felt its belly button? No, you haven’t, because you can’t feel it. And unless you’re a veterinarian or are in desperate need of a hobby, you have never shaved its tummy and visually found it either. Mammal belly buttons tend to be like scars – smoothed over and lintless. Our belly buttons, on the other hand, tend to be much more morphologically well-defined. Easy to see. Easy to feel. Why is ours so conspicuous?

Third, it is generally a bad idea to have skin with an inward divot or outward protuberance. Divots are potential places for infection, and protuberances are at extra risk of abrasion. That’s why the skin over your entire body tends to be divotless and protuberanceless. “Smooth” is good for skin and the bodies they cover, so the fact that belly buttons stick their noses up at this design criterion may suggest they have a reason for existing. That is, it seems to indicate that there is a good reason for belly buttons…a reason good enough to outweigh the disadvantage of having a divot or protuberance.

So, there is a case to be made that morphologically visible belly buttons may be selected for in humans. They could be covered over but are not in us, they in fact are covered over in other animals, and there is an apparent disadvantage to having them.

But what on Earth could belly buttons be for? I don’t know, although my suspicion is that it is linked in some way to sexual selection, and to the fact that we’re the naked upright ape. Other animals’ belly buttons would not be visible to anyone because of fur or because of its being located on the underside, or both. But in our case we’re naked and standing upright, so our navel is something others can potentially see. I have argued elsewhere (“The Hue Of Hefner: How Color Made An Empire Possible“) that perhaps we’re the naked ape because we are color signaling over our entire bodies, not just the face; could it be that the navel is somehow part of the socio-sexual signaling we engage in?

It has not passed my notice, in this light, that the belly button is definitely sexy. Not everything that’s visible on our bodies is necessarily considered sexy; e.g., eyebrows, nostrils and elbows get few fetish videos made about them…I am told. But we can be shy about our belly buttons, and perhaps that is a hint as to what they’re doing there.

Mark Changizi is a professor of cognitive science at Rensselaer Polytechnic Institute, and the author of The Vision Revolution (Benbella Books).

Read Full Post »

Originally a piece in ScientificBlogging, October 2, 2009…

Dear Hugh Hefner:

Ever wondered  why you’re rich?   Yes, yes, you’re a savvy businessman who succeeded where thousands have failed.   But there are deeper reasons underlying why your business model works at all. When one digs deeply enough one finds that color – yup, the stuff of rainbows and Crayola – is at the core of your success. Without hue, there’d be no Hugh.

To see why you should be giving thanks to the existence of color, let’s start with something closer to your home; nakedness.   Although mammals tend to be furry-faced, some of us primates had the chutzpah to lose the hair on our faces, and often on our rumps. And we humans are nearly naked all over, something you may have noticed.   If we humans weren’t so bare, we would probably not wear robes. And then there would be no reason to disrobe.

If there were no bare skin, there would  be no Hefner as we know it.

Now  let’s delve deeper and ask why some of us primates got bare in the first place. One feature that distinguishes the primates with bare faces from the furry-faced ones is color vision. The naked primates can see in color, but the furry-faced ones cannot.   Color goes with nudity. Why?

As I have argued in my research, our color vision is a distinctive kind of color vision, one that is specialized for detecting the color changes that happen in skin due to the physiological changes in blood (e.g., oxygenation). Most varieties of color vision – like that in birds, reptiles and bees – do not have this extraordinary capability. Our color vision is for seeing blushes, blanches, red rage, sexual engorgement and the many other skin color changes that occur as one’s emotion, mood, or physiology alters. Color is for seeing embarrassment, fear, anger, sexual excitement, and so on.

Our primate ancestors once had furry faces, and one was born with our style of color vision, able to detect the peculiar changes in our underlying blood physiology. Although the faces this ancestor looked at were  furry, some skin would have been visible, such as around the eyes, nostrils, lips and any lighter patches of fur. This ancestor would have been born an “empath,” able to see the moods of others. Color vision of this kind would thus spread over time.

And once it spread, animals could then have evolved to “purposely” signal colors indicating their mood, and then bare skin would have evolved to have more canvas for signaling. Many of our skin color changes are indeed “purposeful,” i.e., not simply inevitable consequences of our underlying physiological state. For example, Peter D. Drummond has shown  that peoples’ faces blush more on the side which people can see.

You might be wondering  why, unlike the other primates who mainly have bare faces and rumps, we humans are so naked all over.  It might be that, although we don’t consciously notice it, we color signal over our entire canvas.  If all our bare spots are for color signalling (setting aside the palms and the bottoms of the feet) then we should not be naked in places that viewers would not tend to be able to see.

Well, there are three places on the body that are difficult to observe; the top of the head, the underarms and the groin. And notice that, as expected if bare skin is for color signaling, these three spots are the universally furry spots on humans.

The only complication here is that the groin does occasionally become dominated by bare skin rather than fur, namely when  the genitalia engorge. But at these times there is often another person involved in a behavior wherein the groin is, ahem, no longer difficult to see.

Bare skin really may be for looking at! And it is worth  looking at because it often signals something to the viewer. But the viewer can only see these signals if they have our special kind of color vision.

No color vision, no nakedness. No nakedness, no Hugh Hefner.

Or, no hue, no Hugh.

And now the real point of my writing: Because of the dependency of your enterprise on the evolution of color, it would only be natural to bring some diversity to those apocryphal parties at the mansion … by inviting an evolutionary neuroscientist.

Just have your people call my person.

Mark Changizi is a professor of cognitive science at Rensselaer Polytechnic Institute, and the author of The Vision Revolution (Benbella Books).

Read Full Post »