In three experiments, perceived vertical and horizontal distances in outdoor settings were investigated. Horizontal distances were adjusted by 70 subjects to make them appear equal to vertical distances ranging from 2 to 47 m. The results showed that (1) the matched horizontal distance is represented as a linear function of vertical distance; (2) the slope of the linear function is generally larger than unity, suggesting that when vertical distance is physically equal to horizontal distance, vertical distance appears larger than horizontal distance; (3) physiological muscular variables such as eye, head, and body position are not crucial in judging vertical and horizontal distances; (4) vertical distance of a building appears larger when viewed from afar than when viewed from nearby. 151The purpose of this study was to determine whether, in outdoor settings, horizontal distance or vertical distance would appear to be longer. We refer to horizontal distance as the distance along the ground surface and vertical distance as the distance along the direction of gravity . An example of horizontal distance is the distance from an observer to a building, and an example of vertical distance is the height of the building. Figure I shows four different viewing positions from which comparisons of vertical and horizontal distances can be made. Figure la illustrates the look-up condition, with the subject standing near the base of the building; Figure lb illustrates the look-at condition, with the subject standing on the ground away from the building; Figure lc illustrates the look-down condition, with the subject on the roof or a floor of the building looking down at the ground; Figure Id illustrates the Iie-down condition, with the subject lying on his/her back near the base of the building.A number of studies have been performed under the look-up and lie-down conditions. Morinaga (1935) showed that for a vertical standard distance of 1 m in the look-up condition, the matched horizontal distance increased by 4 % to 14% and did not change substantially with the position of eye and head. Makishita (1947, Experiment 1) determined equidistant curves as a function of elevation angle in the look-up condition, and showed that the matched vertical distance was smaller than the matched horizontal distance. Osaka (1947) demonstrated that for vertical standard distances of 4 to 12 m, the matched horizontal distance increased by 12%to 21 %in the lookup condition, but that this trend disappeared when the sub-

In many conventional image recognition methods, distances among pixels are rarely taken into consideration explicitly because images are processed in the form of vectors. Then the nunber of connection among pixels is in direct proportion to that squared of pixels. It is thought that this problem may be got over by reducing connections among distant pixels, for correlations among neighboring pixels are larger than among distant pixels in general images. This idea is realized by methods based on the autonomous decentralized system. This research is the first try to solve the problem of figure-ground separation for dynamic image with this method. The separation mentioned above is to extract the part (figure) at where motion velocity is different from the background (ground) in the dynamic image. This process consists of two phases. First we execute provisional separation using spatial differences of optical flow calculated locally at each pixel. Unfortunately, this provisional separation by local operation may include certain classification error. Then next we correct them by dynamical interactions among neighboring pixels. Now, problem of explosion in number of connection among pixels never occur because this recognition system is realized with Ginzburg-Landau equation which can be calculated by local operations. This recognition system is superior in error ratio to the method based on Bayes decision which uses global information and is the best method of linear separation. Furthermore, this system can execute the separation of dynamic image made of random dot pattern which have been thought to be difficult to separate.

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