Does perceived steepness deter stair climbing when an alternative is available?
Psychonomic Bulletin & Review (2014) - Comment
pubmed: 24197656  doi: 10.3758/s13423-013-0535-8  issn: 1531-5320  issn: 1069-9384 

Frank F. Eves, Susannah K. S. Thorpe, Amanda Lewis, Guy A. H. Taylor-Covill