Abstract
In this study, we compared younger and older observers' ability to judge slant from texture gradients, velocity gradients, and disparity gradients. The observers viewed planar surfaces that were presented at four different slants (20, 35, 50, & 65 degrees from fronto-parallel). The observers viewed the surfaces through a circular occluding aperture. The resulting visible patterns subtended 21.8 degrees of visual angle. Each of the older (aged 61 to 82 years) and younger observers (aged 18 to 26 years) made five judgments for each experimental condition. The observers made their judgment on each trial by adjusting the slant of a palm board until it matched the perceived slant of the depicted surface. In general, the older observers' judgments of slant were just as accurate as those produced by the younger observers. In all cases, the observers' perceived slants increased as a function of the actual slants. The rate of increase in perceived slant relative to changes in actual slant (i.e., the slope of the best-fitting regression lines) was higher for the texture gradients than for the velocity and disparity gradients. The results indicate that texture gradients contain a large amount of information about surface slant and that they are just as informative (and may even be more informative) than either velocity or disparity gradients.