1996 年 15 巻 1 号 p. 9-31
The literature concerning aperture viewing or anorthoscopic perception is extensively reviewed, and it is mathematically explained why the figure passing behind the slit is perceived as distorted. First, the basic assumption of the theory is that the distortion ratio of the figure is determined by the ratio of the apparent velocity devided by the actual velocity (Rock, 1981). Second, the velocity of the figure needs to be computed because the aperture problem must be solved to perceive the figure anorthoscopically (Shimojo & Richards, 1986). Third, the slope of the line-segment within the slit may not be veridically perceived because the acute angle between the slit and the figure may be overestimated (Helmholtz, 1909/1962). As a result, the computed velocity of the figure is constantly overestimated, which results in the elongation of the figure. Fourth, because the figure abruptly appears and disappears within the slit, the perceptual system does not follow the abrupt change of the velocity so that the transit time to travel across the slit may be constantly overestimated, which results in the shrinkage of the figure. As the result of the compound effects of these, the figure behind the slit may sometimes be elongated and sometimes be shrinked. The distortion ratio is suggested to be a hyperbolic function of the transit time.