The concave "waste mold" image on the left was produced as a mold for making a bronze casting. When viewed from a distance, especially with one eye closed, the image appears to be a normal, convex sculpture similar to the rubber image on the right. However, when the viewer moves left or right of the image, the concave face appears to follow.
This exhibit illustrates one type of optical illusion: we see what we expect to see! We expect faces to be convex, so our eye-brain system interprets the concave mold to be convex. We expect the nose to be closest to us, so as we move the orientation of the nose causes us to interpret the face as following us.
Applications, Connections & Extensions:
When a person rides in a car, nearby objects seem to whiz by, while distant scenery is so far off that it seems to follow the car. In the same way, the nose on the concave mask is farthest from us so it seems to follow us as we walk by.
See the Connections Exhibit, the Mysterious King Tut, for another example of a face which seems to turn as we move.
The concave mold on the left was created by artist David Seagraves. The convex rubber "sculpture" on the right was created by a New Trier High School art teacher to allow students to compare the convex and concave images.