Segregation of motion structure from random visual noise.

A potential source of information about spatial layout, surface slant, and self-motion is provided by transformations of the optic flow field. Theoretical analyses have demonstrated that such flow fields can be decomposed into translation, rotation, expansion, and deformation components. The objective in this study was to investigate the effectiveness of these motions as visual primitives for preattentive scene segregation. The stimuli consisted of two-frame patterns containing 998 dots. A variable number of these dots (5 to 50) were defined as target dots, representing a specific motion structure, with the residual dots defined as a noise field. The observers' task was to identify the location and type of motion structure. On the basis of the number of target dots needed to detect and correctly identify the target structure, it was determined that translation was the most easily detected structure, followed by rotation, expansion, and compression. Deformation was found to have a detection threshold as high as compression. The results are related to other studies of these motion components.