Look at this guy.
He is half-smiley, half-frowny. I drew the mouth carefully to make it equal parts sad and happy.
But when you look at him — take him in whole — would you say he's having a good day or a bad day?
Most people would say: good day. He seems a little more smiley than not.
That's because, says science writer Sam Kean, when we look at somebody, the left side of that person's face is more emotionally powerful and "determines the overall emotional tenor."
So if his left side is happy and his right side is sad, left wins — the whole face feels happy-ish. What is equal is made unequal. It's as if when I look at you, instead of taking you in with one visual gulp, I'm scanning your face from left to right and the left side feels more dominant.
Why would that be?
Well, when you look at someone, your right brain is doing most of the work. That's the side of your brain that specializes in faces and is extra good at reading emotions.
But — as you probably know — your right brain operates mainly through the left side of your body. So when you look at someone's face, your right brain pulls in information from the left of your visual field. Which means you will notice more, read more and remember more about the left side of that person's face. His right side matters less.
If you were to see a photo of that person later, and cut it in half, you'd think, "Oh, this guy looks more like his left side." That's because your brain tricked you to think that way.
In his new book, The Tale of the Dueling Neurosurgeons, Sam Kean says this habit of "looking left" has profoundly affected the world of art — especially portrait painting.
People who sit for artists, he says, seem to have a sense that the left side of their face is going to pack more emotive power and make a bigger impression than the right side. This is almost certainly not a conscious thought, but if you look systematically at enough paintings, you'll see a clear, telltale pattern.
In portrait after portrait, you find that subjects, instead of looking dead on at the viewer ...
... they will face slightly sideways to give their left side more exposure.
Mona Lisa is a famous example. She (or was it Leonardo?) decided to turn her face ever so slightly, exposing more left cheek.
Jean-Pierre Muller/AFP/Getty Images
How big is the "show-us-your-left" bias? Well, if sitters behaved totally randomly, you'd expect to see the three basic options equally often: 33 percent would face the audience, 33 percent would turn left, 33 percent would turn right.
But when scholars looked, that's not what they found. One study of 1,474 portraits painted in Europe from the 16th to the 20th centuries found that roughly 60 percent showed the sitter favoring the left side of the face — men 56 percent of the time, women 68 percent. Another study looked at 50,000 objects from the stone age to the present and found that after the early Greeks, there was a consistent left-profile bias. When it comes to Jesus suffering on the cross, the tilt is dramatic: Jesus' head is shown facing left more than 90 percent of the time.
The "show-us-your-left" bias, Sam writes, "held, no matter whether the artists themselves were left- or right-handed."
We don't know if the artists told their models, "I want you to look to the left," or if the sitters chose this posture to display their more expressive side. "But the bias seems universal," Sam writes. He points out that when the sitter turns, the left eye moves toward the center of the canvas, like this ...
... which then puts most of the sitter's face on the left side, where, says Sam, "the face-hungry right hemisphere can study it."
When Doesn't This Happen?
There are exceptions, of course. Leonardo da Vinci, who painted Mona Lisa, often went the other way and produced lots of right-facing portraits.
Self-portraits, it seems, often face right. But, Sam says, "Artists tend to paint self-portraits in the mirror, which makes the left half of the face appear on the right side of the canvas. So this 'exception' might actually confirm the bias."
Curiously, Sam found that prominent scientists, at least in their official portraits for the Royal Society in England, usually face right. "Perhaps they simply preferred to seem cooler and less emotional — more the stereotypical rationalist."
A skeptic might say this is learned behavior. You go to art school or become an apprentice — the boss turns his subjects to show more left cheek, so you pick up the habit. So that's what this is: a habit. And maybe a Western habit. Western languages, after all, read left to right. In Arabic, the language (and the faces?) might go the other way.
Sam considered this, but he found "surveys of portraits in Egypt (where texts read right to left) turned up a healthy majority of left-facing portraits as well."
What about children's drawings? Kids haven't been exposed to adult paintings, museum art, cultural cues — they just grab crayons and draw. Do they draw faces looking left?
They do, says Sam. Most kids — especially the righties — draw people facing left. "Overall culture probably influences the direction of portraits somewhat," he wrote, "but most artists naturally highlight the left side."
This analysis left me thinking: When you imagine an artist and model sitting quietly in the studio, it looks so quiet, so ... dull. But if Sam's idea is right, the two of them are actually doing battle.
The artist's right brain is looking at the model's left side. The model's right brain is murmuring "paint my left," but what's left to the painter is right for the model, so the two of them are pushing at each other, the model twisting to her left, giving the artist less of what the artist wants, the artist, presumably, focusing on what the model is showing less and less of. What looks so serene, is, perhaps, a ruthless tug of war, the artist saying "Give me more left!", the model saying, "I'm giving you left — but it's my left!"
Art. I always knew it was a sweaty business.
Sam Kean's new book The Tale of the Dueling Neurosurgeons: The History of the Human Brain as Revealed by True Stories of Trauma, Madness, and Recovery, is a history of brain science — a chapter-by-chapter drama of how you and I learned what's in our brain, how it works, what happens when it doesn't. Mostly it's a series of short stories featuring vivid moments of discovery. Kings get lanced through the head, and the court doctor leans in for a look; presidential assassins are executed, and scientists wonder, "Why did he do that? Did his brain make him kill?" From these tales, Sam builds us our brain. (Sam, I should mention, is a regular contributor to Radiolab.)
Speaking of which (Radiolab, I mean), I will be giving a public talk Saturday night (May 10) in Woods Hole, Mass., should you be in the vicinity. It's a benefit for Atlantic Public Media — the wonderful folks who run Transom, who teach the radio arts and who pilot WCAI. I'm calling the talk "Saddam Hussein's Secret Octopus and Other Tales of Science." I'll be on stage at 7:30 p.m. at the Marine Biology Lab's Lillie Auditorium, 7 MBL St.