FIGURE 3.20 Which Tabletop Is Longer? The Shepard Tables illusion consists of two tables that are oriented in different directions. It capitalizes on our automatic use of depth perception cues to perceive what is really a two-dimensional drawing as three-dimensional objects. By relying on these well-learned depth perception cues, most people pick (b) as being the longer tabletop. In contrast, Mike May was oblivious to the perceptual illusion. He correctly responded that the two tabletops were the same size and shape (Fine & others, 2003). You can verify this with a ruler.

Source: Information from Shepard (1990).