Wobble cones and wobble holes: the stereokinetic effect revisited.

It is well-known that patterns of eccentric circles when slowly rotated give rise to compelling three-dimensional impressions of cones or conical holes which can 'wobble' as the pattern rotates. The wobble can be considered as part of the overall phenomenon of depth elicited from a rotating display, the 'stereokinetic' effect (SKE). This paper considers the three-dimensional appearance as being the result of the sliding of contours and thus it imitates the motion parallax found in real three-dimensional objects in motion. New variants of SK figures are used to examine these points. An analogy with computer programs is proposed which questions earlier views on the location of perceptual invariance.