A comparison of global motion perception using a multiple-aperture stimulus.

The human visual system integrates local motion signals to generate globally coherent motion percepts. However, it is unclear whether the perception of different types of global motion relies on a common motion integration mechanism. Using the multiple-aperture stimulus developed by K. Amano, M. Edwards, D. R. Badcock, and S. Nishida (2009), we compared the motion sensitivity (in terms of coherence threshold) for translational, circular, and radial motion. We found greater motion sensitivity for the two complex (circular and radial) motion types than for translational motion, implying that specific motion integration mechanisms are involved in the computation for different motion types. Our results reveal a "complexity advantage" in perceiving motion, which is consistent with physiological and computational evidence suggesting that specific mechanisms exist for processing complex circular/radial motion. We further examined the contributions of several critical factors that influence human global motion sensitivity. We found that human sensitivity for all motion types remained constant across a range of motion sampling density but varied depending on global speed. The minimum stimulus duration required for observers to reach constant sensitivity was found to be short ( approximately 140 ms) for all motion types.