Roger Shepard’s Greatest Optical Illusion

How the brilliant cognitive scientist turned the tables on us all with an illusion that defies our logical understanding

A creative illustration of the Shepard tabletop illusion. The actual illusion appears below. (Source, modified by Author)

“Reality is merely an illusion, albeit a very persistent one.” — Albert Einstein (1879–1955)

A while back, I wrote an article about an audio illusion known as Shepard Tones, first described in 1964 by renowned cognitive scientist and psychologist, Roger N. Shepard (see “If Escher Made Music”). In the course of researching that article, I became more familiar with the incredible breadth and depth of his work.

Background: Mental Rotation

Shepard studied physics at Stanford University and, in 1955, he obtained his Ph.D. in psychology at Yale. He was fascinated by human perception — how we see, hear, and understand the world around us. Back in the 1950s, psychology was primarily focused on behaviorism, the study of observable behaviors as exemplified by the work of Ivan Pavlov and B.F. Skinner.

Ever inquisitive, Shepard was more interested in the science of what occurs inside our heads. In 1958, he joined Bell Labs, where he began to explore the idea that our perception is not simply a passive process, but rather, a highly active one. He understood that the…