“…To examine if there is substantial group difference between children skilled in mental abacus and their peers on non-symbolic number sense, some important cognitive factors would be controlled. The factors included general intelligence (Cowan & Powell, 2014;Fuchs, Fuchs, Compton, Hamlett, & Wang, 2015;Jordan et al, 2013), visuospatial processing ability (Boonen, van Wesel, Jolles, & van der Schoot, 2014;Kyttala et al, 2014;Looi et al, 2017;Swanson, Jerman, & Zheng, 2009), processing speed (Berg, 2008;Bull & Johnston, 1997;Fuchs et al, 2006), and language processing (Hecht, Torgesen, Wagner, & Rashotte, 2001;Purpura & Ganley, 2014;Wei, Yuan, Chen, & Zhou, 2012). It is to ensure that group difference in approximate number sense originates from mental abacus experience rather than outperformances of the cognitive factors.…”