Enigma

From Michael’s “Visual Phenomena & Optical Illusions”

Stare at the centre of the figure for a while. Some ‘scintillating’ activity will build up in the violet and blue annuli. Some observers also report a circular rotation within these regions; things will begin to “run around in circles”.

This image “The Enigma” is by Isia Leviant (1981), Palais de la Découverte, Paris.

Comment.

Mechanism currently unknown (as far as I know, but see Zanker 2004), an ‘enigma’. Activity in MT (Zeki, 1993) is an interesting finding, but does not ‘explain’ the effect IMHO.

Sources

Leviant I (1982) Illusory motion within still pictures: The L-effect. Leonardo 15:222–223

Zeki S, Watson JD, Frackowiak RS (1993) Going beyond the information given: the relation of illusory visual motion to brain activity. Proc R Soc Lond B Biol Sci 252:215–22

Leviant I (1996) Does ‘brain-power’ make Enigma spin? Proc R Soc London B 263:997–1001

Barch D, Kumar T & Glaser DA (2003) Modeling the illusory motion of Enigma with an excitable neuronal array [Abstract]. Journal of Vision, 3:72a

Zanker J (2004) Naturwissenschaften 91:149–156 [PDF]