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).

Comment.

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

Source

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]