The Perception of Distance on a Real Geographic Slope

Ooi, Wu, and He (2001) have shown that for objects resting on flat, horizontal surfaces, those that appear in the lower sector of the visual field are perceived as close to the observer and objects located near the visual horizon are perceived as further from the observer. Researchers have hypothesized that observers utilize the angle subtended between the horizon and the line of sight to the target object as information for distance.In a previous investigation Hajnal, Bunch, and Kelty-Stephen (2014) showed that an object’s physical angle of declination below the horizon is not uniquely utilized when making distance estimates to objects placed on a sloped surface. In that experiment a flat, horizontal surface was visible in the background when viewing objects placed on the sloped surface. To further investigate the possible utility of the angular declination below the horizon hypothesis we have replicated the findings of the previous study on a natural hillside where a flat, horizontal surface is not visible in the background. This setup has allowed us to evaluate whether observers rely on the same information to perceive distance on ramps versus real hills. The present research may have implications for the hypothesis which claims that perceived effort influences space perception (Proffitt, 2006a, 2006b) in addition to optical variables