Studying some temporal aspects of stereoscopic processing in order to clarify phenomena of stereoscopic persistence and investigate how the brain deals with stereoscopic stimuli that involve various types of clues or difficulties. It was early realized by Exner in 1875 that stereopsis could occur when both eyes together receive the two images of a stereo pair one after the other. Stereopsis occurs even when a void interval is inserted between the presentations of each image. For instance, Ogle found that stereopsis occurred when two 18 ms presentations were separated by a void interval of 100 ms. Stereopsis has also been studied with protocols in which the two images of a stereo pair were presented cyclically, in alternation to the two eyes