Effects of adaptation to apparent movement on recovery of structure from motion.

Past work on the recovery of three-dimensional structure from dynamic two-dimensional images has led to inconsistent conclusions regarding the contributions of the short-range and long-range motion processes. In the present experiments, subjects adapted to displays (either four lines or 50 randomly positioned pixels) whose spatiotemporal parameters were chosen to favor either the short-range or long-range process. Adaptation periods were followed by test displays that simulated the rotation of a four-pixel random object about the vertical gamma-axis. The dependent measure was the angle of rotation between successive frames of the rotation display at which percepts of three-dimensional structure broke down. Both the original data and derived measures based on best-fitting polynomials showed small but consistent effects: Compared to control conditions, adaptation to short-range motion reduced the angle at which percepts of structure broke down; adaptation to long-range motion increased them. It is suggested that both low-level (i.e. short-range) and high-level (long-range) processes contribute to the recovery of structure from motion.