THE DISTANCE USED FOR SCALING DISPARITIES IS THE SAME AS THE ONE USEDFOR SCALING RETINAL SIZE

To determine the physical size and global three-dimensional (3-D) shap e of an object, retinal size and retinal disparity have to be scaled i n accordance with the object's distance. We examined whether the dista nce used for scaling retinal disparity is the same as the distance use d for scaling retinal size, Subjects adjusted the 3-D shape (size and depth) of a computer-simulated ellipsoid to match a tennis ball, Analy sis of the errors when only the ellipsoid was visible in an otherwise completely dark room suggests that the distance used for scaling retin al disparity is indeed the same as that used for scaling retinal size, This was confirmed by showing that the correspondence between the dis tance used for scaling retinal disparity and that used for scaling ret inal size does not improve when more information about distance is ava ilable (room lights on), although both distances are then much closer to the simulated distance, Finally, we show that this correspondence i s not due to the use of distance-invariant higher order binocular info rmation. (C) 1997 Elsevier Science Ltd.