Investigating What Optical Texture Property is Used for Relative Distance Perception

Bingham et al. (2022) investigated which property of the texture on a support surface is used to perceive relative distance and found it was the texture image shape. We further investigated the use of image shape by manipulating texture image size and the aspect ratio of optical texture elements. Methods: Participants matched the distance (TD) of a target by moving a hand avatar with both appearing on different side-by-side textured support surfaces in a virtual display. While texture elements on the left remained 3cm squares, elements on the right varied in three conditions: (1) Identical Texture, right elements same as left; (2) Different Size (DS), right element sized 0.6/0.8/1/1.2/1.4 relative to left; (3) Aspect Ratio (AR), image width or height altered so image width/height = 0.6/0.8/1/1.2/1.4 on the right. Results: multiple regressions showed that in the width AR manipulation, TD was significant (p < 0.001, F = 243.98), but neither AR (p > 0.07) nor the interaction (p > 0.3) was. In the height AR manipulation, TD was significant (p < 0.001, F = 869.17) as was AR (p = 0.009, F = 3.64), but the interaction (p > 0.7) was not. In the DS manipulation, TD was significant (p < 0.001, F = 904.84) as was DS (p < 0.001, F = 5.64), but the interaction (p > 0.2) was not. Conclusions: Variations in the size of the texture elements influenced relative distance perception. However, when manipulating aspect ratio, changes in the width were not significant, while the image height was, which is consistent with Chen & Saunders (2020) showing that compression of optical texture was used in slant perception. Reconsidering Bingham et al. (2022), we concluded that the relative compression of optical texture (image height) is used as monocular information about relative distance.