The taller you are, the smaller the world appears: perceptual distortion of binocular space depends on the size of personal body space

摘要

It has been theorized that our body serves as a reference frame in visual perception of sizes and distances. In support of this claim, indirect experimental evidence shows that induced modification of peripersonal space, for example through tool use (Witt, Profitt, and Epstein, 2005) or ownership of magnified/shrunken body parts (van der Hoort, Guterstam, and Ehrsson, 2011), results in modified perception of objects size or egocentric distances. However, direct measures in support of this hypothesis was previously lacking; here we found that scaling of depth from stereo depends on the size of the peripersonal space by testing disparity scaling directly with short and tall observers (corresponding to smaller and larger peripersonal space respectively), without manipulating subjecta??s perceived personal space. Participants adjusted the depth of a virtual 3D three-rod configuration, in which one central rod was offset in front of two flanking rods, until they perceived a perfect equilateral triangle. Stimuli in this visual depth estimation task were presented in the dark such that stereo cues were isolated. Simulated distance of the stimulus was randomly generated from five possible values (28cm, 46cm, 64cm, 82cm and 100cm). The results were grouped according to height (SHORT: 150h160 cm and TALL: 173h190 cm). As expected, all subjects demonstrated a lack of shape constancy, as perceived depth of the three-rod configuration decreased with increased distance. More remarkably, findings showed that short observers perceive larger depth extents than tall observers (p 0.03), indicating that scaling distances of tall observers were smaller than those of short observers. These results suggest that scaling of disparities is dependent on the extent of peripersonal space; indeed, this implies that scaling distances within the same external space are more compressed for people with larger body morphologies.