Abstract
The spatial factor in Korte's third law has been regarded as the apparent (rather than retinal) separation between two light spots, by Ogasawara (1936), Oba (1957), and Attneave and Block (1973). This position was re-examined in three experiments, using five to 10 subjects. When two light spots placed in physically different depths were presented to both eyes in a dark room, they appeared as a light spot moving tridimensionally. But even when apparent motion was perceived tridimensionally, the optimal ISI in this law was not affected by the apparent separation as far as the retinal separation was constant. The optimal ISI in this situation seems to be determined by the separation between the stimulated positions in retina, not by the apparent separation. Korte's law in the dark room represents a function of the peripheral motion detective system rather than the central synthetic system.
