Discrimination of rotation from linear motion: influence of interference gratings and dichoptic viewing

Observers viewed a screen on which a number of patches containing horizontally moving pixels were presented. Target patches consisted of pixels whose motion simulated the rotation of a cylinder around its Y-axis; distractors, of pixels whose motion was linear. The task was to assess whether a display contained a target patch. Exp. 1 showed that the superposition of the displays with drifting sine-wave gratings interfered with rotation detection in a spatial- and temporal-frequency specific manner. In Exp. 2, dichoptic presentation greatly reduced the interference of the drifting gratings. It is argued on various grounds that the process(es) responsible for the detection and discrimination of rotating structure in depth exists at a low level of the visual system.