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I have a book all about optical illusions that has a picture with the same effect...except it's of Maggie Thatcher *shudder*.
[Happosai]
( ,
Tue 24 May 2005, 0:16,
archived)
[Happosai]
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I guess none of you lot have studied undergraduate psychology of perception recently.
The original article is by Peter Thompson, "Margaret Thatcher: a new illusion."
Perception 9:483–484 (1980).
Search google for "thatcher illusion" and you can see various demonstrations...
but still, woo!