Localization of the start and the end point of a moving stimulus path during eye tracking

The subjects track visually a smoothly moving light target which increases its brightness at a definite point in the visual field and after traversing a path with a definite length, again decreases its brightness to the initial level. The subjects' task is to localize the start and the end point of this path. Systematic misperceptions are observed in the performance of the task, influenced by the position of the stimulus in the visual field and by the length of the path. The mislocation of the end point of the stimulus path is algebraically smaller than the mislocation of the start point. The data are not in agreement with the hypothesis that the visual system first determines the path length and then determines the path position as a whole. The most probable assumption is accepted to be that the processes of localization of the start and the end point of the path are not independent.