Zachary is looking at a reversible figure which first appears to be a vase, and then appears to be two faces. His perception of the figure keeps switching between these two interpretations. What causes the switch in perception?

Question

Quizplus · Accepted Answer

Reversible figures often have an ambiguous figure-ground distinction, which causes the switch in perception from one interpretation to another. The viewer sees the figure as one thing (e.g. a vase) until the background becomes the foreground and the figure becomes something else (e.g. two faces). The lack of a clear figure-ground distinction makes it difficult for the viewer's brain to settle on one interpretation, causing the switch in perception.

Zachary Is Looking at a Reversible Figure Which First Appears