Spatial integration of visual motion with separate speed and direction information

We present evidence to support the possibility that motion information is divided into two scalars: direction and speed, to integrate local motions over a wide spatial range. With various motion stimuli composed of numerous red and green dots, observers perceived that peripheral dots moved similar to central dots on the basis of the same direction or speed, even when speed or direction was different. The results indicate that the direction and speed of local motion can be processed separately and that the distributions are analyzed independently to integrate the local motions. This process, based on two motion scalars, may be useful for the perception of complex motions that would be difficult to perceive with a process based on motion vectors.