Rubin's vase

Page numbers are for draft copy at present; they will be replaced with correct numbers when final book is formatted. Chapter numbers are correct and will not change now.

Rubin's vase is an ambiguous image, which can be seen as vase or as two faces looking at one another. Human viewers tend to see such images flip quasi-periodically between the two interpretations: vase, then faces, then vase again ... This gives clues as to how the brain deals with ambiguity and hence lessons for computer disambiguation.

Used on Chap. 22: page 540