HOW MUCH OF THE VISUAL OBJECT IS USED IN ESTIMATING ITS POSITION

Localization accuracy for a wide Gaussian bar(sigma 1 degrees) was ess entially invariant with sampling density over a wide range. Luminance contrast, on the contrary, had a profound effect on localization accur acy. This difference suggests that the position is estimated from a fe w (3-4) samples from all those available in the image. A subsequent ex periment confirmed that limiting the display to four samples did not i mpair localization accuracy. Computer simulations show that the result cannot be explained by the peak or centroid rule for position. The re sults imply that the visual system uses only a few samples to interpol ate the luminance profiles, regardless of how many samples are availab le in the image. (C) 1998 Elsevier Science Ltd. All rights reserved.