Abstract
Gibson's ground theory of space perception (1950) places the density gradient of a surface at the center of distance perception, such that (1) the rate of change in the density of the texture elements of a surface specifies the orientation and slant of a surface relative to an observer, and (2) the magnitude change in density of texture elements surrounding an object compared to the density near the observer specifies that object's distance from the observer. Sinai, Ooi, and He (1998) investigated this theory as it relates to how the brain might exploit this cue to simplify computations of distance. Their investigations found that observers were more accurate in judging absolute distance, measured by blind-walking, when objects were viewed on a surface of homogenous texture (i.e., continuous texture gradient), as opposed to a surface of heterogenous texture (i.e., an interruption of texture gradient caused by a gap in the surface). Here, we seek to extend this investigation to the perception of an object's reach-ability. We suspect that continuous texture gradient may be critical in the successful realization of certain affordances (Gibson, 1979). In a table-top reaching task, participants were asked to judge whether an object was reachable in two conditions: (1) when the object rested on a surface with a continuous texture gradient and (2) when the object rested on a surface with an interruption in the texture gradient (i.e., two distinct gradients). Results showed that participants overestimated action capabilities in both conditions, but less so in the heterogeneous condition. As a consequence, participants in the heterogenous condition were also more accurate with respect to their capabilities. This comports with Sinai, Ooi, & He's findings that distance estimates across discontinuous gradients are smaller than those made across continuous gradients.
Meeting abstract presented at VSS 2017