Visual Perception of Bending Motion

Principles of the perception of a special kind of partially rigid motion—bending motion—are explored. The proximal stimuli consisted of an outline quadrangle with various combinations of changes of length and direction of the four sides. The result demonstrated a perceptual preference for rotary motion over bending motion, and of bending motion over two-dimensional form change (stretching). The principle of minimum object change can predict this result, implying that rotation, bending, and stretching are perceptually preferred in this order.