“…It should be said that the GIE was introduced as a measure of spatial complexity following Cordier and colleagues [1][2][3][4] and has since been adapted to investigate skill [4,5], practice [4] and route design [6] effects. To be clear, your concerns have been discussed elsewhere and for a full theoretical treatment I refer you to Cordier s 1994 and 1996 papers, both, published in Human Movement Science [1,4] (and see also [3]). Aside from its theoretical consistency, a main interest of adapting GIE is, that, according to Cordier et al [4] the GIE can assess the spatial fluency of the climbed trajectory.…”