Motion and shape in common fate.

We determined how much motion coherence was needed to detect a target group of four moving dots in a dynamic visual noise (DVN) background. The lifetimes of the trajectories of the target and that of the noise dots were the same. In addition to parallel trajectories and collinear dot arrangements, divergent, convergent, or crossing trajectories and non-collinear dot arrangements were also tested. Performance saturated at a lifetime of approximately 600 ms. It was best for parallel trajectories and collinear dots, and worse for crossed trajectories with non-collinear dots, where it approached performance in a no-motion, form-only control experiment. Results illustrate the importance of common fate in motion perception in DVN, when other factors are equated.