The eyes have it: exposure times and saccadic movements in visual half-field experiments.

Several tachistoscopic visual half-field experiments using exposure times in excess of 150 msec have been reported and arguments have been put forth justifying this procedure. An experiment was done investigating visual field accuracy under conditions where eye movement was allowed, following parafoveal exposure. Two control experiments were done to evaluate the viewing conditions. When eye movement is permitted, accuracy in both visual fields reaches 100%. It is concluded that visual field differences found with exposure times greater than 150 msec are due to the active cooperation of the subjects and not due to the justifications advanced by experimenters using long exposure times.