Abstract
A single experiment compared younger and older observers' ability to judge slant from natural patterns of optical texture. The observers monocularly viewed four differently textured planar surfaces that were presented at four different slants (20, 35, 50, & 65 degrees from fronto-parallel). Three of the textures were flat (marble, granite, and a random array of circular elements), while the remaining pattern possessed solid texture elements (i.e., pebbles). The observers viewed the textured patterns through a circular occluding aperture. The resulting visible textures subtended 20 degrees of visual angle. Each of the 36 older (aged 61 to 78 years) and younger observers (aged 18 to 27 years) performed five judgments for each of the 16 combinations of slant and texture type. The observers made their judgment on each trial by adjusting the slant of a palm board until it matched the perceived slant of the textured pattern. In contrast to previous research with computer-generated textures (e.g., Rosas, Wichmann, & Wagemans, 2004; Todd, Thaler, & Dijkstra, 2005), our observers did not show underestimation in their slant estimates. In general, the observers' perceived slants were close to the actual slants (except for the circle texture where the observers overestimated by an average of 8.2 degrees). For two of the texture types (marble and granite) the younger observers perceived more slant than the older observers, whereas the two age groups performed similarly for the circle and pebble textures. The precision (i.e., reliability across repeated judgments) of the younger observers' judgments was the same for all texture types. The precision of the older observers' judgments, in contrast, was significantly better for the circle and pebble textures and poorer for the marble and granite textures. The overall results indicate that the ability to perceive slant from optical texture remains relatively intact with increases in age.