Errors in direction-of-motion discrimination with dichoptically viewed stimuli

At durations shorter than about 150 msec, a complex grating comprising a static 1-c/deg grating and a moving 3-c/deg grating is perceived as moving in the direction opposite that of the physical direction of motion. Here the phenomenon is further examined by measuring the perceived direction of motion of the fused images of a 1-c/deg grating presented to one eye and a moving 3-c/deg grating presented to the other. The strength of the illusion is almost unaffected by dichoptic presentation. This observation is consistent with the hypothesis that perceived motion is a consequence of the way the visual system integrates signals arising from different detectors tuned to the two component gratings.