Thomas Harp, David Bressler, and David Whitney (2007)
Position shifts following crowded second order motion adaptation reveal processing of local and global motion without awareness.
Journal of Vision 7(2):1-13.
Adaptation to first-order (luminance defined) motion produces not only a motion aftereffect but also a position aftereffect, in which a target pattern's perceived location is shifted opposite the direction of adaptation. These aftereffects can occur passively (when the direction of motion adaptation cannot be detected) and remotely (when the target is not at the site of adaptation). Although second-order (contrast defined) motion produces these aftereffects, it is unclear whether they can occur passively or remotely. To address these questions, we conducted two experiments. In the first, we used crowding to remove a local adapter's second-order motion from awareness and still found a significant position aftereffect. In the second experiment, we found that the direction of motion in one region of a crowded array could produce a position aftereffect in an unadapted, spatially separated region of the crowded array. The results suggest that second-order motion influences perceived position over a large spatial range even without awareness.