Conjuring Credits

The Origins of Wonder

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Geometric Shapes Psychological Force

When asked to draw a simple geometric design, the most popular choice is a triangle. If asked to draw two simple geometric designs, most people will choose a triangle and a circle. This information was included in a routined group of psychological forces based on ideas by John Mulholland and recorded by John Norther Hilliard in notes he made for a proposed chapter on the psychology of magic that was never written for his Greater Magic, published in 1938. Hilliard's notes are undated but were probably made in the early 1930s. They were finally published in the “More Greater Magic” section of the Kaufman 1994 edition of Greater Magic, p. 1157. Hilliard describes the two designs being drawn one below the other.

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.