In this paper, we discuss perceptive properties of people based on experiments by means of sequentially presenting pairs of pictures to an observer on a computer terminal.Observers are inquired whether they believe the subjects in the picture to have stayed in the same position or have changed positions, and if changed, whether they moved forward or backward and by how much. The precedent picture (called the standard picture) of each of paired pictures to be presented is taken of a person standing at fixed points of 9m, 13.5m and 27m in front of a camera. The antecedent one (referential one) is selected from the pictures that are taken of the same person who has slightly moved positions (0.5m, 1m, 1.5m in case of 9m standard position) in these three types of forward positions and three types of backward positions. We have some interesting results from the experiments concerning perception of forward/backward movement of a person. The results indicate that humans perceive a person to be approaching an observer more sensitively and accurately than that of a person departing from the observer. A result shows that the amount of perspective movement is closely related to the ratio of the size of person's images in the paired pictures. Additionally, observers estimate less of a change in movement at the farther points than from nearer points, and the background scene scarcely gives any effects on the estimation of the movement.
