Wikimedia Commons
Wikimedia Commons

How Did Humans Learn to Paint in Three Dimensions?

Wikimedia Commons
Wikimedia Commons

If you begin clicking through The Portrait Project's timeline, a strange thing starts to happen around the 1300s. The flat, childish depictions of kings and saints begin to change. Their faces start to curve, ever so slightly, into what looks like a third dimension. Noses begin to have shading and depth. The Christ child begins to look like he's being held by his mother, not sitting flush with her. The portraits are still flat and unnatural, but not nearly as primitive as the portraiture that came before them.

Then come the 1400s, and suddenly portraits become people. They pop off the canvas in variations of darkness and light, their faces detailed and proportioned.

I was puzzled by this. Being able to paint in three dimensions is not like being able to build a car. For a car to work, you must learn thousands of separate skills and concepts, from how to make steel to how to drill for oil, and then piece them precisely together. Those processes took thousands of years to culminate in Karl Benz's Motorwagen and Henry Ford's Model T.

But to paint photo-realistically—that's different. It seems like a simple matter of sweeping your paint brush a different direction, of using darker paint for shadow and making things smaller if they're far away. How could the artists of the first millennia and before not know how to do this? It's as if the knowledge hung there in the air, unseen or ignored.

Or did it?

Art History

James G. Harper is a professor at the University of Oregon who specializes in the history of Renaissance art. According to Harper, the first misconception is that humans never knew how to draw in 3D before the 1300s. He points to the work of ancient Romans in the Pompeian Second Style wall paintings and the 8th century illuminated manuscripts, the Coronation Gospels of Charlemagne, which, although primitive, show clear use of realism and perspective.

The real reason that three-dimensional art was seldom seen before the 14th century was that artists didn't want to portray life in three dimensions. Harper explains: "In the medieval period artists lost the desire to make lifelike images. The job of art was not to reproduce the real world, but instead to show another world. Unshackled from the mundane task of realism it entered a more expressive realm."

Western Civilization after the fall of the Roman Empire was miserable, riddled with plague and hunger and oppression. People of the Dark Ages were simply waiting out their time on this mucky rock called Earth until they could be called to Heaven. And it was the surreal unknown of Heaven that most strongly influenced their work.

Gradually, artists lost the knowledge required to render realistic imagery. Says Harper: "Bit by bit, (artistic) training stopped including things like perspectival composition or the modeling of 3D forms through the modulation of light and shadow. To regain that, one would have to retrain oneself."

That retraining was sparked by the Renaissance. Renaissance means rebirth, a finding value in the old ways. The ancient world was re-examined and revived, one facet being the desire to paint realistically. Simultaneously, as the works of the great ancient philosophers were being widely read, the individual self became interesting again. The human form and the life within it became worthy of close examination and accurate reproduction.

A 13th century painter named Giotto was on the forefront of this revolution. As one 17th century biographer said, Giotto initiated "the great art of painting as we know it today, introducing the technique of drawing accurately from life." He laid the groundwork of realistic painting that has touched every artist from Michelangelo to Thomas Kinkade.

The mathematical precision that later artists would use to bring proportion to their canvases was slower to develop. "For modeling with light and shadow (as well as psychological realism) Giotto is a great artist to consider," Harper says. "But mathematical perspective was truly lost, and though Giotto understood that diagonal lines signaled spatial depth, it was not until Brunelleschi's c. 1410 experiment that they understood it systematically."

There isn't a single reason Western Civilization suddenly gained (or regained) the ability to paint in three dimensions. It came about through the retrieval of old ideas and the birth of brand new ones. People began to see life as more than just God's desperately uncomfortable waiting room. Artists began to observe the essence and detail that filled their actual lives, and, as artists must, brought what they saw into the light.

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How Does Catnip Work?

If you have a cat, you probably keep a supply of catnip at home. Many cats are irresistibly drawn to the herb, and respond excitedly to its scent, rubbing against it, rolling around on the floor, and otherwise going nuts. There are few things that can get felines quite as riled up as a whiff of catnip—not even the most delicious treats. But why does catnip, as opposed to any other plant, have such a profound effect on our feline friends?

Catnip, or Nepeta cataria, is a member of the mint family. It contains a compound called nepetalactone, which is what causes the characteristic catnip reaction. Contrary to what you might expect, the reaction isn’t pheromone related—even though pheromones are the smelly chemicals we usually associate with a change in behavior. While pheromones bind to a set of specialized receptors in what’s known as a vomeronasal organ, located in the roof of a cat's mouth (which is why they sometimes open their mouths to detect pheromones), nepetalactone binds to olfactory receptors at the olfactory epithelium, or the tissue that lines the mucus membranes inside a cat’s nose and is linked to smell.

Scientists know the basics of the chemical structure of nepetalactone, but how it causes excitement in cats is less clear. “We don’t know the full mechanisms of how the binding of these compounds to the receptors in the nose ultimately changes their behavior,” as Bruce Kornreich, associate director of the Cornell Feline Health Center, tells Mental Floss. Sadly, sticking a bunch of cats in an MRI machine with catnip and analyzing their brain activity isn’t really feasible, either from a practical or a financial standpoint, so it’s hard to determine which parts of a cat’s brain are reacting to the chemical as they frolic and play.

Though it may look like they’re getting high, catnip doesn’t appear to be harmful or addictive to cats. The euphoric period only lasts for a short time before cats become temporarily immune to its charms, meaning that it’s hard for them to overdo it.

“Cats do seem to limit themselves," Michael Topper, president of the American Veterinary Medical Association, tells Mental Floss. "Their stimulation lasts for about 10 minutes, then it sort of goes away.” While you may not want to turn your house into a greenhouse for catnip and let your feline friend run loose, it’s a useful way to keep indoor cats—whose environment isn’t always the most thrilling—stimulated and happy. (If you need proof of just how much cats love this herb, we suggest checking out Cats on Catnip, a new book of photography from professional cat photographer Andrew Martilla featuring dozens of images of cats playing around with catnip.)

That said, not all cats respond to catnip. According to Topper, an estimated 70 percent of cats react to catnip, and it appears to have a genetic basis. Topper compares it to the genetic variation that causes some individuals to smell asparagus pee while others don’t. Even if a cat will eventually love the smell of catnip, it doesn’t come out of the womb yearning for a sniff. Young kittens don’t show any behavioral response to it, and may not develop one until several months after birth [PDF].

But some researchers contend that more cats may respond to catnip than we actually realize. In one 2017 study, a group of researchers in Mexico examined how cats might subtly respond to catnip in ways that aren’t always as obvious as rolling around on the floor with their tongue hanging out. It found that 80 percent of cats responded to catnip in a passive way, showing decreased motor activity and sitting in the “sphinx” position, an indicator of a relaxed state.

There are also other plants that have similar effects on cats, some of which may appeal to a wider variety of felines than regular old catnip. In a 2017 study in the journal BMC Veterinary Research, researchers tested feline responses to not just catnip, but several other plants containing compounds similar in structure to nepetalactone, like valerian root, Tatarian honeysuckle, and silver vine. They found that 94 percent of cats responded to at least one of the plants, if not more than one. The majority of the cats that didn’t respond to catnip itself did respond to silver vine, suggesting that plant might be a potential alternative for cats that seem immune to catnip’s charms.

Despite the name, domestic cats aren’t the only species that love catnip. Many other feline species enjoy it, too, including lions and jaguars, though tigers are largely indifferent to it. The scent of the plant also attracts butterflies. (However, no matter what you’ve heard, humans can’t get high off it. When made into a tea, though, it reportedly has mild sedative effects.)

The reason Nepeta cataria releases nepetalactone doesn’t necessarily have to do with giving your cat a buzz. The fact that it gives cats that little charge of euphoria may be purely coincidental. The chemical is an insect repellant that the plant emits as a defense mechanism against pests like aphids. According to the American Chemical Society, nepetalactone attracts wasps and other insect predators that eat aphids, calling in protective reinforcements when the plant is in aphid-related distress. That it brings all the cats to the yard is just a side effect.

Because of this, catnip may have even more uses in the future beyond sending cats into a delighted frenzy. Rutgers University has spent more than a decade breeding a more potent version of catnip, called CR9, which produces more nepetalactone. It’s not just a matter of selling better cat toys; since catnip releases the compound to ward off insects, it’s also a great mosquito repellant, one that scientists hope can one day be adapted for human use. In that case, you might be as excited about catnip as your cat is.

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Why Are Mugshots Made Public Before a Suspect is Convicted by the Court?

Jennifer Ellis:

Several reasons.

1. Mugshots can help find people when they have absconded, or warn people when someone is out and dangerous. So there is a good reason to share some mugshots.

2. Our legal system requires openness as per the federal constitution, and I imagine most if not all state constitutions. As such, this sort of information is not considered private and can be shared. Any effort to keep mugshots private would result in lawsuits by the press and lay people. This would be under the First and Sixth Amendments as well as the various Freedom of Information Acts. However, in 2016 a federal court ruled [PDF] that federal mugshots are no longer routinely available under the federal FOIA.

This is partially in recognition of the damage that mugshots can do online. In its opinion, the court noted that “[a] disclosed booking photo casts a long, damaging shadow over the depicted individual.” The court specifically mentions websites that put mugshots online, in its analysis. “In fact, mugshot websites collect and display booking photos from decades-old arrests: BustedMugshots and JustMugshots, to name a couple.” Some states have passed or are looking to pass laws to prevent release of mugshots prior to conviction. New Jersey is one example.

a) As the federal court recognizes, and as we all know, the reality is that if your picture in a mugshot is out there, regardless of whether you were convicted, it can have an unfortunate impact on your life. In the old days, this wasn’t too much of a problem because it really wasn’t easy to find mugshots. Now, with companies allegedly seeking to extort people into paying to get their images off the web, it has become a serious problem. Those companies may get in trouble if it can be proved that they are working in concert, getting paid to take the picture off one site and then putting it on another. But that is rare. In most cases, the picture is just public data to which there is no right of privacy under the law.

b) The underlying purpose of publicity is to avoid the government charging people and abusing the authority to do so. It was believed that the publicity would help protect people. And it does when you have a country that likes to hide what it is up to. But, it also can cause harm in a modern society like ours, where such things end up on the web and can cause permanent damage. Unfortunately, it is a bit of a catch-22. We have the right to know issues and free speech rights smack up against privacy rights and serious damage of reputation for people who have not been convicted of a crime. The law will no doubt continue to shake out over the next few years as it struggles to catch up with the technology.

This post originally appeared on Quora. Click here to view.


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