SEGREGATION BY COLOR AND STEREOSCOPIC DEPTH IN 3-DIMENSIONAL VISUAL SPACE

Two experiments were conducted to investigate how color and stereoscop ic depth information are used to segregate objects for visual search i n three-dimensional (3-D) visual space. Eight observers were asked to indicate the alphanumeric category (letter or digit) of the target whi ch had its unique color and unique depth plane. In Experiment 1, distr acters sharing a common depth plane or a common color appeared in spat ial contiguity in the xy plane. The results suggest that visual search for the target involves examination of kernels formed by homogeneous items sharing the same color and depth. In Experiment 2, the xy contig uity of distracters sharing a common color or a common depth plane was varied. The results showed that when target-distracter distinction be comes more difficult on one dimension, the other dimension becomes mor e important in performing visual search, as indicated by a larger effe ct on search time. This suggests that observers can make optimal use o f the information available. Finally, color had a larger effect on sea rch time than did stereoscopic depth. Overall, the results support mod els of visual processing which maintain that perceptual segregation an d selective attention are determined by similarity among objects in 3- D visual space on both spatial and nonspatial stimulus dimensions.