Conjuring Credits

The Origins of Wonder

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Geometric Shapes Psychological Force

The psychological force of one simple geometric shape inside another seems first to have been described by Robert Nelson in his 1957 monograph, Miracles of the Mind. Nelson claimed that the choice most spectators would make was a triangle inside a square.

James Randi reported that Uri Geller performed a variant of this force at least as early as 1972 (see Randi's Magic of Uri Geller, 1975, p. 296). Geller steered the choice to a triangle inside a circle by cautioning the spectator not to pick a square, as that was “too easy.” Geller's connection with this force was first mentioned in print by Martin Gardner in his “Mathematical Games” column in Scientific American, Vol. 229. No. 2, Aug. 1973, pp. 98 & 101.