Riener, C. R., Stefanucci, J. K., Proffitt, D. R., &Clore, G. (2011). An effect of mood on the perception of geographical slant. Cognition and Emotion, 25(1), 174-182.

Previous research has shown that hills appear steeper to those who are fatigued, encumbered, of low physical fitness, elderly, or in declining health (Bhalla & Proffitt, 1999; Proffitt, Bhalla, Gossweiler, & Midgett, 1995). The prevailing interpretation of this research is that observers’ perceptions of the environment are influenced by their capacity to navigate that environment. …