Compare the two tables in the figure above, on the left one lies a wooden panel. Which would be easier to get through a narrow door? How do size and shape of the two table tops compare?
Now either tick the ‘Run’ checkbox, or click and drag the wooden panel on top of the right table. Since it simultaneously rotates, it’s somewhat tricky to get right.
The two table tops certainly do not look alike!
This phenomenon plays on the interchange of 2- and 3-dimensional interpretation of the figure. In the real-world scene, the tables certainly have a different shape. In that sense this not really an illusion, rather a “trick” by intermingling image space (the 2-dimensional screen in front of you) and object space (the “real” tables). It certainly reveals that our brain can appropriately deduct 3-d object properties from 2-d drawings.
Roger N. Shepard originated this one among a number of beautiful illusions, which he drew himself; many of which are now “floating around the internet” without proper attribution (e.g., the elephant with the impossible feet), his “Terror Subterra” is also in the present collection. He also invented the “ever rising scale” auditory illusion.
The original of the present illusion is called “Turning the Tables”.
Shepard RN (1981) Psychological complementarity. In: Kubovy M & Pomerantz JR (eds) Perceptual organization. 279–342. Hillsdale, NJ: Lawrence Erlbaum Associates
Shepard RN (1990) Mind Sights: Original Visual Illusions, Ambiguities, and other Anomalies, New York: WH Freeman and Company
Further artwork of Roger Shepard at Impossible World