“…Many algorithms have been proposed for the detection and localization of object boundaries from motion discontinuities, which detect these boundaries either before, during, or after the computation of 2-D image velocities (for example, Reichardt & Poggio, 1980;Hildreth, 1984;Adiv, 1985;Thompson, Mutch & Berzins, 1985;Schunck, 1986;Spoerri & Ullman, 1987;Hutchinson, Koch, Luo & Mead, 1988;Waxman & Wohn, 1988;Wohn & Waxman, 1990; for review, see Hildreth & Koch, 1987). Heuristics have been suggested for distinguishing stationary and selfmoving objects (Jain, 1984;Heeger & Hager, 1988;Zhang, Faugeras & Ayache, 1968;Burt, Bergen, Hingorani, Kolczinski, Lee, Leung, Lubin & Schvaytser, 1989;Enkelmann, 1990;Frazier & Nevatip, 1990;Nelson, 1990;Thompson & Pong, 1990), some of which are basc,' .-thc behavio.…”