IS STEREOPSIS EFFECTIVE IN BREAKING CAMOUFLAGE FOR MOVING TARGETS

It has been suggested that breaking camouflage is one of the major fun ctions of stereopsis (Julesz, 1971), In this study, we found that ster eopsis is less effective in breaking camouflage for moving targets tha n for static ones, Observers were asked to detect a single dot moving on a straight trajectory amidst identical noise dots in random motion, In the three-dimensional (3D) condition, the noise dots filled a cyli ndrical volume 5.7 cm in height and diameter; the trajectory signal do t moved on an oblique 3D trajectory through the center of the cylinder , In the two-dimensional (2D) control condition, observers viewed one half-image of the 3D cylinder binocularly, Surprisingly, trajectory de tection in the 3D condition was only slightly better than in the 2D co ndition, Stereoscopic tuning for motion detection was also measured wi th a novel target configuration in which the random motion noise was p resented in two depth planes that straddled the fixation plane where t he trajectory target was presented, As the disparity between the noise planes and the fixation plane was increased, trajectory detection imp roved, reaching a peak between 6 and 12 arcmin, and then declining to the 2D level at larger disparities, where the noise became diplopic, S imilar tuning measurements were made for detecting a static pattern, a string of five aligned dots presented in the fixation plane between t wo planes of static noise dots, Adding disparity to the noise planes p roduced a far greater improvement in static detection than in motion d etection, for a comparable range of disparities (1.5-12 arcmin), We sp eculate that the temporal characteristics of the stereo system are not well suited for responding to moving targets, with the result that st ereo does not greatly enhance motion detection in noise. (C) 1997 Else vier Science Ltd.