Abstract

We have investigated the perceived rigidity of rotating ellipses in a variety of conditions, following Wallach et al. (1956), who observed that rigidity is seen only when the eccentricity or aspect ratio is large. We measured the degree of rigidity as a function of aspect ratio, and found that a number of factors besides aspect ratio can have a profound effect on the percept. For example, a single rotating ellipse is often perceived to be more rigid than a family of concentric ellipses of the same aspect ratio. In a similar finding, we have observed that an asymmetric Gaussian blob with elliptical contours is seen to be more rigid than a single ellipse, suggesting that low-frequency content may be important for rigidity.

© 1991 Optical Society of America