Apparent Depth Threshold for the Benussi Effect
Using the single staircase psychophysical method, the apparent depth threshold for the Benussi effect was determined for 5 observers. The threshold occurred at an eccentricity of 2r/3, where r equals the radius of the larger circle expressed in millimeters.
Shape, Height and Angular Movement in Stereokinesis
Cues affecting the apparent height (depth) of a stereokinetic ‘cone’ were investigated by comparing heights for pairs of rotating figures. Apparent height was shown to be independent of the number of bands on the figure and of the geometric perspective by which it was drawn. On the other hand, apparent height was strongly dependent on eccentricity within the figure, with maximum apparent height being achieved at full eccentricity. The reason for the existence of such a definite maximum remains obscure.
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.