Visual search for motion-form conjunctions: Is form discriminated within the motion system?

Motion-form conjunction search can be more efficient when the target is mov ing (a moving 45 degrees tilted line among moving vertical and stationary 4 5 degrees tilted lines) rather than stationary. This asymmetry may be due t o aspects of form being discriminated within a motion system representing o nly moving items, whereas discrimination of stationary items relies on a st atic form system (J. Driver & P. McLeod, 1992). Alternatively, it may be du e to search exploiting differential motion velocity and direction signals g enerated by the moving-target and distractor lines. To decide between these alternatives, 4 experiments systematically varied the motion-signal inform ation conveyed by the moving target and distractors while: keeping their fo rm difference salient. Moving-target search was found to be facilitated onl y when: differential motion-signal information was available. Thus, there i s no need to assume that form is discriminated within the motion system.