Phenomenal regression to the frontal and natural picture.

The retinal image of a figure on a slanted picture is narrower than that of a figure on a frontal picture. In this study, the perceived width of various figures (horizontal line segments, ellipses, faces, symbolic faces, and artistic pictures) on a slanted picture plane was measured. The width of the figures was magnified or reduced in order to vary the naturalness of the original figures. The perceived width was found to be much closer to the width of the original figures than to the retinal images of the slanted figures. The width of the original figures was also found to affect the perceived width of the slanted figures; the perceived width was observed to be more biased toward a more natural width. On the other hand, the naturalness of the figures did not affect the perceived slant. These results suggest that the visual system corrected the width of the figures on a slanted plane, taking into the account naturalness or prägnanz as well as the slant.