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David Bunch, Alen Hajnal, Damian Stephens, Attila Farkas, Andras Csanadi; The Perception of Distance on a Slope. Journal of Vision 2012;12(9):908. doi: 10.1167/12.9.908.
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© ARVO (1962-2015); The Authors (2016-present)
Ooi, Wu, and He (2001) demonstrated that observers rely on angular declination below the horizon (ADBH) to determine distance on horizontal terrain. The ADBH hypothesis states that an object’s distance can be determined by d = h/tan(α), where d is the distance to the object, h is the observer’s eye height, and α is the ADBH corresponding to the object (Figure 1). Thus, objects close to the horizon appear further away and those further from the horizon appear closer to the observer. Would the ADBH hypothesis apply to targets placed on sloped surfaces? We hypothesized that objects on a sloped surface should be perceived as further away than objects placed at the same distance on a horizontal surface. Participants estimated the distance to a cone on a ramp laid flat or elevated at either 5 or 10 degrees (Figure 2). Participants viewed the cone, placed a blindfold over their eyes, turned 180 degrees, and walked a distance they believed replicated the distance previously viewed. Distance estimates became exaggerated as surface inclination and target distance increased (Figure 3). Blind walking may have introduced a perceptual distortion, but another alternative might be that we simply did not present the data using specifying variables. We recast the actual and perceived object location as an ADBH, scaled to eyeheight. Perceived ADBH mapped 1-to-1 onto actual ADBH irrespective of surface slope (Figure 4), consistent with the hypothesis that ADBH is invariant, body-scaled information for distance perception. Is reliance on ADBH based only on perception, cognition, or both? Participants both observed and responded to targets on a 10 degree slope significantly longer than on other surfaces (Figure 5). Any extra time devoted to observation and responding did not influence the quality and nature of reliance on specifying information, thus obviating the need for cognitive interpretations.
Meeting abstract presented at VSS 2012
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