Physical ability, fatigue, bodily changes and stress all links with psychological approach and how we perceive our environment - an article in the recent issue of Perspectives on Psychological Science elaborates.
The author finds that we have a natural tendency to view hills as steeper when we are tired, less physically able, or carrying a heavy load. Likewise, inclines appear greater and the distance to the ground appears further when there is a perceived risk of injury. The author attributes this perceptual variance to our instinctive need to conserve energy and protect ourselves from harm.
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Participants were asked to estimate the steepness of hills, both from the bottom and at a cross-section, before and after a physically demanding run. The results displayed a trend for participants to estimate the steepness of the hill as greater after completing the run. Similar over-estimation occurred when participants were asked to estimate the steepness of hills when wearing a heavy backpack, or when the participant was elderly or otherwise less physically able.
Another experiment placed participants at the top of a hill steep hill, standing on a skateboard. The perceived risk of bodily injury led the participants standing on skateboards to estimate the slope of the hill to be greater than their counterparts on secure ground. The author concludes that 'what one sees in the world is influenced not only by optical and ocular-motor information, but also by one's purposes, physiological state, and emotions.'