English: A photograph of Ian P. Howard, from 2009, taken by Hugh R. Wilson. Howard is shown in front to various concave objects and is holding a concave face of Einstein. Although the Einstein mask is concave, it appears convex, an example of perceptual ambiguity and an illusion. Howard was concerned with these areas, among others, in his research
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The copyright holder, Hugh R. Wilson, gave me written permission (18 Jun 2013) to upload the file and to allow it to go essentially into the public domain. The image may be used freely providing its creator, Hugh R. Wilson, is cited, under
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