Optic flow velocity profiles influence heading and speed discrimination

It is usually assumed that the human visual system is most sensitive to the velocity of motion at the retina. However, two optic flow velocity profiles that specify the same peak velocity can have different durations and specify very different accelerations and displacements of the observer. We compare heading and velocity discrimination in response to constant and raised cosine optic flow velocity profiles. The experiment was divided into four separate blocks, heading discrimination and velocity discrimination, with constant and raised cosine velocity profiles. On each trial, subjects were presented with two consecutive movements (same velocity profile) through a limited lifetime 3-D star field and asked to indicate which motion was more to the right (heading discrimination) or which had a faster maximum velocity (velocity discrimination). The heading experiments show there is not a consistent preference of motion profile within the group but individual subject‘s thresholds are significantly different between motion profile conditions. The different profiles in the velocity experiments did not show as clear a pattern of results as those in the heading experiments