Vision: A Window on Consciousness; The Hidden Mind; Special Editions; by Nikos K. Logothetis; 8 Page(s)

When you first look at the center image in the painting by Salvador Dali reproduced at the right, what do you see? Most people immediately perceive a man's face, eyes gazing skyward and lips pursed under a bushy mustache. But when you look again, the image rearranges itself into a more complex tableau. The man's nose and white mustache become the mobcap and cape of a seated woman. The glimmers in the man's eyes reveal themselves as lights in the windows—or glints on the roofs—of two cottages nestled in darkened hillsides. Shadows on the man's cheek emerge as a child in short pants standing beside the seated woman—both of whom, it is now clear, are looking across a lake at the cottages from a hole in a brick wall, a hole that we once saw as the outline of the man's face.

In 1940, when he rendered Old Age, Adolescence, Infancy (The Three Ages)—which contains three "faces"—Dali was toying with the capacity of the viewer's mind to interpret two different images from the same set of brushstrokes. More than 50 years later, researchers, including my colleagues and me, are using similarly ambiguous visual stimuli to try to identify the brain activity that underlies consciousness. Specifically, we want to know what happens in the brain at the instant when, for example, an observer comprehends that the three faces in Dali's picture are not really faces at all.