“…There have been a few experiments reported in the literature in which human observers have made accurate judgments of 3-D metric structure from motion (Johnston et al, 1994;Lappin & Ahlström, 1994;Lappin & Love, 1992), but they have all involved one of the two special cases identified above. A more typical result in the vast majority of experiments on this topic is that judged metrical relations almost always deviate significantly from the physically specified structure and that they are often unreliable as well (Bocheva & Braunstein, 2000;Bradshaw et al, 2000;Braunstein & Andersen, 1984;Braunstein et al, 1993;Braunstein & Tittle, 1988;Caudek & Proffitt, 1993;Cornilleau-Pérès & Droulez, 1989;Domini & Braunstein, 1998;Domini & Caudek, 1999;Domini, Caudek, & Proffitt, 1997;Durgin et al, 1995;Eagle & Blake, 1995;Hogervorst & Eagle, 1998;Liter & Braunstein, 1998;Liter, Braunstein, & Hoffman, 1993;Loomis & Eby, 1988Norman & Lappin, 1992;Norman & Todd, 1993;Norman, Todd, & Phillips, 1995;Perotti, Todd, Lappin, & Phillips, 1998;Tittle et al, 1995;Todd, 1984Todd, , 1985Todd & Bressan, 1990;Todd & Norman, 1991;Todd & Perotti, 1999;Turner & Braunstein, 1995;Werkhoven & van Veen, 1995). The relative scaling of height, width, and depth reported in these studies can vary dramatically depending on the details of each individual experiment.…”