But this reflex can be manipulated. Expose the chicks to a fake beak—say, a wooden stick with a red dot that looks like the one on the end of an adult herring gull's beak—and they peck vigorously at that, too. Should the chicks see a wood stick with three red dots, they peck even faster. Abstracting and exaggerating the salient characteristics of a mother gull's beak strengthens the response. The phenomenon is known as the "peak-shift effect," since a peak pecking response comes from a shifted stimulus. In it lies one of the core principles of visual art.

The Truth in the Lie

In 1906, Pablo Picasso was determined to reinvent the portrait and push the boundaries of realism, and one of his early subjects was Gertrude Stein. After months in his Paris studio, carefully reworking the paint on the canvas, Picasso still wasn't satisfied. He didn't finish the painting until after a trip to Spain.

What Picasso saw there that affected him so deeply has been debated—the ancient Iberian art, the weathered faces of Spanish peasants—but his style changed forever. When he returned to Paris, he gave Stein the head of a primitive mask. The perspective was flattened and her face became a series of dramatic angles. Picasso had intentionally misrepresented various aspects of her appearance, turning the portrait into an early work of cubist caricature.

Despite the artistic license, the painting is still recognizable as Stein. Picasso took her most distinctive features—those heavy, lidded eyes and long, aquiline nose—and exaggerated them. Through careful distortion, he found a way to intensify reality. As Picasso put it, "Art is the lie that reveals the truth."

What's surprising is that such distortions often make it easier for us to decipher what we're looking at, particularly when they're executed by a master. Studies show we're able to recognize visual parodies of people—like a cartoon portrait of Richard Nixon—faster than an actual photograph. The fusiform gyrus, an area of the brain involved in facial recognition, responds more eagerly to caricatures than to real faces, since the cartoons emphasize the very features that we use to distinguish one face from another. In other words, the abstractions are like a peak-shift effect, turning the work of art or the political cartoon into a "super-stimulus."