Do Subliminally Presented Objects Potentiate Motor Responses

The dorsal visual stream has been implicated in visually guided motor behavior (Milner & Goodale, 1996). Can objects that are nondetectable (subliminal) activate the dorsal stream? Using the stimulus-response compatibility paradigm, a physical correspondence between stimulus and response yields faster reaction times (RTs), we briefly presented images of objects that afford a motor response: common graspable objects (Study 1; reaching and grasping) and indexical pointer finger (Study 2; orienting eye movement). When the orientation of the object and the response side were congruent, RTs were significantly faster than when they were incongruent even though the objects were not detected. This finding suggests that the dorsal stream processes information about the orientation of stimuli that are not consciously perceived and is consistent with the spared ability of blindsight patients.