Separate presentation of additional accelerating motion does not enhance visually induced self-motion perception

It has been repeatedly reported that visual stimuli containing ajittering/oscillating motion component can induce self-motion perception more strongly than a pure radial expansion pattern. A psychophysical experiment with 11 observers revealed that the additional accelerating components of the visual motion have to be convoluted with the motion of the main-axis to facilitate self-motion perception; additional motion presented in an isolated fashion impairs the perception of self-motion. These results are inconsistent with a simple hypothesis about the perceptual mechanism underlying the advantage of jitter/oscillation, which assumes that the accelerating component induces an additional self-motion independently of the main motion at the first stage, and then the two self-motions induced by the main motion and the additional component become integrated.