Getting to Know Da Vinci's Mona Lisa

If you know only one painting in the entire world, it's probably the Mona Lisa (see Figure 1). Her mysterious, intimate smile draws an estimated 6 million visitors to the Louvre Museum in Paris every year. Leonardo painted the Mona Lisa over a period of about four years, starting in 1503. He worked slowly, and the sitter posed for him on more than a few occasions. The portrait immediately brought him fame within Italy.

Unlike many other portraitists of the time, Leonardo didn't sign or date the portrait or reveal the identity of the sitter. However, Leonardo's biographer, Giorgio Vasari, mentions that Leonardo undertook the portrait as a commission from one Francesco del Giocondo (see the following section). This anonymity applies to many of his paintings but confounds both our understanding of them and his evolution as a painter.

Identifying the sitter

Art historians have long debated the identity of the mysterious woman in the Mona Lisa. Was it

• Leonardo's mother?

• A society figure (like Isabella d'Este, Isabella Gualanda, or Cecilia Gallerani)?

• Lisa Gherardini, the wife of a family friend of the da Vincis?

• A Florentine prostitute?

• A disguised self-portrait of Leonardo?

The winning ticket most likely goes to Lisa Gherardini, the lovely wife of a Florentine silk merchant, prominent politician, and two-time widower, Ser Francesco del Giocondo. (The Mona Lisa has also been called La Gioconda in Italy and La Joconde in France.)

Leonardo painted Lisa when she was 24 years old; she went on to become a virtuous wife and the mother of five kids. (Just in case you're wondering: Mona Lisa's first name wasn't Mona. Mona is short for Monna, or Madonna, which means, in this context, "Italian lady.") Vasari guessed Lisa's identity in 1550, but his opinion — though it came down through the ages — was pooh-poohed for hundreds of years.

Setting the standard for portraiture

The Mona Lisa set the standard for all future portraits (so the experts say, anyway) for many reasons:

• Technique: When Leonardo began painting in oil directly onto the wood, he added weak turpentine, which allowed him to paint many layers of glaze and remodel the face as many times as he liked. The layers of glaze heightened the effect of light and shade (chiaroscuro). The light casts soft, heavy shadows on Lisa's face, which lacks eyebrows; ladies of the time considered shaved eyebrows very attractive. (But the copy of the Mona Lisa in Madrid has eyebrows added!) Leonardo's use of sfumato (the deliberate blurring of lines) both defines and incorporates Lisa into the rolling valleys, rivers, and icy mountains behind her, connecting her with nature.

• Composition: Leonardo relied on a pyramidal design, which gives the painting a great sense of harmony between the sitter and the landscape. For the first time, he adopted the half- to three-quarters length, instead of the bust-size pose, with her sitting sideways. This contrapposto (the twisting of one part of the body away from another part) was a modern development (here Mona Lisa sits sideways but she faces front) and helped establish three-dimensional space.

• Landscape: The Mona Lisa was one of the first portraits to show its subject posed before an imaginary landscape. Lisa (and her hair, which blends into the rock outcroppings) interacts with the landscape in a new way. This landscape, with its rocks and pinnacles, is quintessential Leonardo. Although imagined, it reveals Leonardo's studies of watersheds, plants, and maps. It also stresses his interest in a wild nature that contrasts with orderly human life — both, incidentally, part of a larger (mechanistic) whole. Leonardo considered rocks, for example, not only as decoration, as other artists did, but as part of the earth's bones and caused by the earth's geology. The Mona Lisa thus brings together Leonardo's artistic interest in unifying people and nature.

• The smile: Who can turn it down? Seriously, it embodies how Leonardo captured the complex inner life — and all of Lisa's mysteries — without offering solid proof, or overt symbols, of her inner self.

Smiling or mocking? Some explanations

Around 1550, Vasari described Mona Lisa's smile as "more divine than human." Since then, people have come up with different theories about her mysterious mug:

• She was pregnant (and kind of smug about it, too; her swollen fingers, resting on her stomach, give her condition away).

• She had some sort of facial paralysis, wore away her teeth by grinding them, or suffered from asthma.

• She was an unhappy wife, subject to an impotent, alcoholic, and abusive husband. (According to Vasari, Leonardo hired jesters to entertain her while she sat for him, so she remained merry instead of melancholy.)

• She's really playing a joke on you — the real subject is Leonardo himself (in drag!), and he's trying not to laugh. (If this theory is true, then her smile, in Sigmund Freud's view, signifies an old memory that plagued Leonardo his entire life — his erotic attraction to his mother!)

Of course, not everybody buys these theories. So scientists have come up with a few more reasons for Lisa's smile.

If you stare long and hard at Leonardo's portrait of the Mona Lisa, you'll notice how she smiles at you — and how quickly her smile flickers and disappears. Why is she so fickle? Don't worry. It's not you; it's her. Or, rather, it's you, but not in the way you think.

The science of a smile

Until a few years ago, art historians described Lisa's smile by using the word sfumato: blurry, mysterious, elusive. But now, they have a more scientific explanation. Dr. Margaret Livingstone, a Harvard neuroscientist, attributes Lisa's changing expression to the way your eyes and brain process information. Your eyes have two different regions for seeing. The central part (the fovea centralis) picks out details. The peripheral area, which picks up low spatial frequencies, focuses on motion and shadows. When you look at Lisa's eyes, you have less accurate peripheral vision of her mouth. But you still pick up the shadows from her cheekbones, which suggest that she's smiling. When you focus on her mouth, her cheerful disposition seems to disappear. Other artists who (knowingly or unknowingly) have used this optical illusion include Claude Monet, Chuck Close, and Robert Silvers.

Scientists have another theory for Mona Lisa's mysterious smile, and it has to do with lighting. As Christopher Tyler and Leonid Kontsevich of the Smith-Kettlewell Eye Research Institute in San Francisco claim, variable levels of human noise determine how you interpret her smile. After experimenting with visual noise (the equivalent of white specks, or snow, on TV sets) on an image of the painting, they concluded that noise lifting the edges of Lisa's lips gave her a more cheerful countenance, and noise flattening her lips made her look sadder. The flecks of grayish light also made people change their perception of Lisa as they viewed her. Scientists think this phenomenon has to do with how the brain interprets the flow of light signals in the retina. But research in this area continues.