PERCEIVING GEOGRAPHICAL SLANT

People judged the inclination of hills viewed either out-of-doors or i n a computer-simulated virtual environment. Angle judgments were obtai ned by having people (1) provide verbal estimates, (2) adjust a repres entation of the hill's cross-section, and (3) adjust a tilt board with their unseen hand. Geographical slant was greatly overestimated accor ding to the first two measures, but not the third. Apparent slant judg ments conformed to ratio scales, thereby enhancing sensitivity to the small inclines that must actually be traversed in everyday experience. It is proposed that the perceived exaggeration of geographical slant preserves the relationship between distal inclination and people's beh avioral potential. Hills are harder to traverse as people become tired ; hence, apparent slant increased with fatigue. Visually guided action s must be accommodated to the actual distal properties of the environm ent; consequently, the tilt board adjustments did not reflect apparent slant overestimations, nor were they influenced by fatigue, Consisten t with the fact that steep hills are more difficult to descend than to ascend, these hills appeared steeper when viewed from the top.