“…The present findings are potentially informative for the design and implementation of training studies. Previous research highlighted the positive role of spatial skills for basic number processing (Crollen & Noël, 2015;Thompson et al, 2013) and more complex mathematical calculations and/or mathematical expertise (Geary, Saults, Liu, & Hoard, 2000;Sella, Sader, Lolliot, & Cohen Kadosh, 2016;Wei, Yuan, Chen, & Zhou, 2012; see also review by de Hevia, Vallar, & Girelli, 2008). We show that spatial skills, notably mental rotation, are also important for basic arithmetic, especially at the stage of skill acquisition.…”