NARRATOR：

Listen to part of a lecture in an art history class.

MALE PROFESSOR：

As you know, uh, portrait artists often position their subjects so that their head is turned a little to one side... thereby presenting the artist with a semi-side view, uh a semi-profile view.

And for some reason, Western European artists have historically tended to show the left side of the subject's face more than the right.

Uh, awhile back, some researchers examined about 1,500 portraits, painted from the sixteenth to the twentieth century in Western Europe, and in the majority of them, it's the left side of the face that's most prominently displayed...

[rhetorically] Why's that?

And, interestingly enough, this tendency to show the left side has diminished over time, especially in the twentieth century.

In fact, the left-right ratio is now about one to one, fifty percent left, fifty percent right.

[rhetorically] Why's that?

We do know that for many artists, the choice of left side/right side was very important.

There's an image by the Dutch painter Vincent van Gogh called The Potato Eaters... that shows the profiles of a group of farmers...

It's a lithograph, which is a print made from images drawn on a stone.

When you print something that way, what you get is a mirror image of the original picture—the exact same image, except that left and right are reversed.

And van Gogh was so dissatisfied with the print that he wrote to his brother, quote, "the figures, I'm sorry to say, are now turned the wrong way," end quote.

Anyway, why do you think so many painters in the past chose to depict the left side of their subject's face? Nancy?

FEMALE STUDENT：

Could it have to do with whether the artists were left-handed or right- handed?

Like maybe most of them were right-handed, and maybe for some reason they felt more comfortable painting the left side?

MALE PROFESSOR：

Okay. Many right-handed artists do find it easier to paint left profiles, and many art historians think that's the reason for the directional bias.

But if that hypothesis—let's call it the, uh, the "right-handed hypothesis"—was correct, you'd expect that left-handed artists would find it easier to paint right profiles.

But the research suggests that left-handed artists find it just as easy to paint left profiles as right...

So... any other ideas? [when no ideas are forthcoming, the prof proceeds]

Well, another theory's what's known as the parental imprinting hypothesis... which proposes that people are more used to seeing left profiles, because—[slightly skeptical] supposedly—right-handed parents are more likely to hold their babies in their left arm...

MALE STUDENT：

[providing support for the theory] Well, my sister just had a baby, and she keeps talking about how her left arm is getting so much stronger than her right...

MALE PROFESSOR：

[humorously] Okay, so there's some anecdotal evidence.

FEMALE STUDENT：

[picking up thread of discussion] So then when the baby looks up at their parent, what they see is the left profile.

MALE PROFESSOR：

Right, and—so the theory goes—the left side of the face becomes imprinted in our memories.

FEMALE STUDENT：

But the parental imprinting hypothesis doesn't explain why left profiles have decreased over time.

I mean, parents are still carrying their babies in their left arm, right?

MALE PROFESSOR：

Exactly... [introducing the theory he subscribes to] Alright, what about the way the artist's studio is organized, specifically the light source?

Remember that the light source determines where the shadows are.

So if you're a right-handed artist, you'd want the light coming from your left... because you don't want your painting hand to cast a shadow across your canvas. Right?

And if the light's coming from your left, you'd want your subject to turn to their right, into the light.... And if they do that, what do you see?

FEMALE STUDENT：

The left side of their face.

MALE PROFESSOR：

Exactly. And, well into the twentieth century, many an artist's primary light source would be the sun, and they'd set up their studio to take maximum advantage of it...

But then what happens as other high-quality, portable, artificial light sources become available?

FEMALE STUDENT：

Well, you could position your subject in a lot more different ways and still have good lighting on your subject and on your canvas.

MALE PROFESSOR：

[leading] So...

FEMALE STUDENT：

You'd expect to see a more balanced ratio of left- and right-side portraits.