Latency differences and the flash-lag effect

The tendency for briefly flashed stimuli to appear to lag behind the spatial position of physically aligned moving stimuli is known as the flash-lag effect. Possibly the simplest explanation for this phenomenon is that transient stimuli are processed more slowly than moving stimuli. We tested this proposal using a task based upon the simultaneous tilt illusion. When an oriented stimulus is surrounded by another oriented stimulus, the inner stimulus can appear to be rotated away from the orientation of the surround. By flashing central static sinewave gratings at specific phases of an annular gratings rotation cycle, we were able to determine the temporal dependence of the tilt illusion. Our results suggest a small, approximately 20 ms, processing advantage for the rotating stimulus relative to the flashed stimulus. Such a small advantage, if due to differential latencies, is insufficient to account for the flash-lag effect.