“…Although only few children spontaneously construct viewpoint perspective (i.e., a diagonal spatial axes system in their drawings), it was assumed that nevertheless children would gain a deeper understanding of explicit spatial axes systems while becoming familiar in school with simple measurements of extensions and quantities in vector space. From previous research, we know that children can discriminate perspective, even though they also find the diagonal difficult to construct in drawing tasks other than perspective drawings (Ackermann-Valladao, 1987;Kosslyn, Heldmeyer, & Locklear, 1980;Olson, 1970Olson, /1996Perner, Kohlmann, & Wimmer, 1984). However, when the production obstacle of drawing in perspective was removed by using predrawn axes systems, the majority of 11-year-old children in Study 2 demonstrated their understanding of crossed axes systems by pronounced figure size modification.…”