Unlike the usual setting for aparent visual movement, which is the exposure of two stimuli separated by a temporal interval, this experiment involved Higginson's procedure of simultaneous presentation with initial or terminal overlap. That is, one line was exposed and maintained, and after a time (the time varied from 7.5 to 142.5 ς) a second line a certain distance away was also exposed, and then, after 67.5 ς, the two exposures were simultaneously discontinued; this is "initial overlap." Or, the two lines came on simultaneously, but one was maintained for a longer time; this is "terminal overlap." In either case, movement was reported, though initial overlap was the more favorable condition. The greater the amount of overlap, the greater the number of reports of movement, in a given number of trials; hence it is concluded that the perception of movement is a function of the increase in the temporal variation of one of the stimuli. (PsycINFO Database Record (c) 2006 APA, all rights reserved)